ENGINEERING DRAWING
(NSQF)
1st Year
Common for All Engineering Trades under CTS
(Not applicable for Draughtsman Trade Group)
(For all 1 Year & 2 Year Trades)
DIRECTORATE GENERAL OF TRAINING MINISTRY OF SKILL DEVELOPMENT & ENTREPRENEURSHIP GOVERNMENT OF INDIA
NATIONAL INSTRUCTIONAL MEDIA INSTITUTE, CHENNAI
Post Box No. 3142, CTI Campus, Guindy, Chennai - 600 032 (i) Copyright Free. Under CC BY License. Engineering Drawing (NSQF) - 1st Year Common for all Engineering Trades under CTS (Not applicable for Draughtsman Trade Group)
Developed & Published by
National Instructional Media Institute Post Box No.3142 Guindy, Chennai - 32 INDIA Email: [email protected] Website: www.nimi.gov.in
Printed by National Instructional Media Institute Chennai - 600 032
First Edition :November 2019
Rs.170/-
©
(ii) Copyright Free. Under CC BY License. FOREWORD
The Government of India has set an ambitious target of imparting skills to 30 crores people, one out of every four Indians, by 2020 to help them secure jobs as part of the National Skills Development Policy. Industrial Training Institutes (ITIs) play a vital role in this process especially in terms of providing skilled manpower. Keeping this in mind, and for providing the current industry relevant skill training to Trainees, ITI syllabus has been recently updated with the help of comprising various stakeholder's viz. Industries, Entrepreneurs, Academicians and representatives from ITIs.
The National Instructional Media Institute (NIMI), Chennai, has now come up with instructional material to suit the revised curriculum for Engineering Drawing 1st Year (For All 1 year & 2 year Trades) NSQF Commom for all engineering trades under CTS will help the trainees to get an international equivalency standard where their skill proficiency and competency will be duly recognized across the globe and this will also increase the scope of recognition of prior learning. NSQF trainees will also get the opportunities to promote life long learning and skill development. I have no doubt that with NSQF the trainers and trainees of ITIs, and all stakeholders will derive maximum benefits from these IMPs and that NIMI's effort will go a long way in improving the quality of Vocational training in the country.
The Executive Director & Staff of NIMI and members of Media Development Committee deserve appreciation for their contribution in bringing out this publication.
Jai Hind
RAJESH AGGARWAL Director General/ Addl. Secretary Ministry of Skill Development & Entrepreneurship, Government of India.
New Delhi - 110 001
(iii) Copyright Free. Under CC BY License. PREFACE
The National Instructional Media Institute(NIMI) was set up at Chennai, by the Directorate General of Training, Ministry of skill Development and Entrepreneurship, Government of India, with the technical assistance from the Govt of the Federal Republic of Germany with the prime objective of developing and disseminating instructional Material for various trades as per prescribed syllabus and Craftsman Training Programme(CTS) under NSQF levels.
The Instructional materials are developed and produced in the form of Instructional Media Packages (IMPs), consisting of Trade Theory, Trade Practical, Test and Assignment Book, Instructor Guide, Wall charts, Transparencies and other supportive materials. The above material will enable to achieve overall improvement in the standard of training in ITIs.
A national multi-skill programme called SKILL INDIA, was launched by the Government of India, through a Gazette Notification from the Ministry of Finance (Dept of Economic Affairs), Govt of India, dated 27th December 2013, with a view to create opportunities, space and scope for the development of talents of Indian Youth, and to develop those sectors under Skill Development.
The emphasis is to skill the Youth in such a manner to enable them to get employment and also improve Entrepreneurship by providing training, support and guidance for all occupation that were of traditional types. The training programme would be in the lines of International level, so that youths of our Country can get employed within the Country or Overseas employment. The National Skill Qualification Framework (NSQF), anchored at the National Skill Development Agency(NSDA), is a Nationally Integrated Education and competency-based framework, to organize all qualifications according to a series of levels of Knowledge, Skill and Aptitude. Under NSQF the learner can acquire the Certification for Competency needed at any level through formal, non-formal or informal learning.
The Engineering Drawing 1st Year (Comon for All 1 year & 2 year Engineering Trades under CTS) is one of the book developed by the core group members as per the NSQF syllabus.
The Engineering Drawing (Common for All 1 year & 2 year Engineering Trades under CTS as per NSQF) 1st Year is the outcome of the collective efforts of experts from Field Institutes of DGT, Champion ITI’s for each of the Sectors, and also Media Development Committee (MDC) members and Staff of NIMI. NIMI wishes that the above material will fulfill to satisfy the long needs of the trainees and instructors and shall help the trainees for their Employability in Vocational Training.
NIMI would like to take this opportunity to convey sincere thanks to all the Members and Media Development Committee (MDC) members.
R. P. DHINGRA Chennai - 600 032 EXECUTIVE DIRECTOR
(iv) Copyright Free. Under CC BY License. ACKNOWLEDGEMENT
The National Instructional Media Institute (NIMI) sincerely acknowledge with thanks the co-operation and contribution of the following Media Developers to bring this IMP for the course Engineering Drawing (1st Year (For All 1 year & 2 year Trades)) as per NSQF.
MEDIA DEVELOPMENT COMMITTEE MEMBERS
Shri. M. Sangara pandian - Training Officer (Retd.) CTI, Guindy, Chennai.
Shri. G. Sathiamoorthy - Jr.Training Officer (Retd.) Govt I.T.I, DET - Tamilnadu.
NIMI CO-ORDINATORS
Shri. Nirmalya Nath - Deputy General Manager, NIMI, Chennai - 32.
Shri. G. Michael Johny - Assistant Manager, NIMI, Chennai - 32.
NIMI records its appreciation of the Data Entry, CAD, DTP Operators for their excellent and devoted services in the process of development of this IMP.
NIMI also acknowledges with thanks, the efforts rendered by all other staff who have contributed for the development of this book.
(v) Copyright Free. Under CC BY License. INTRODUCTION
Theory and procedure along with the related exercises for further practice This book on theory and procedure along with related exercises contains theoretical information on 1st year Engineering drawing (for engineering trades of 1 year and 2 year) and procedure of drawing/ sketching different exercise for further practice are also available. Wherever required, BIS specification has been used.. Exercise for further practice The practice exercise is given with Theory and procedure for 1st Year book made obsolete as it was felt that, it is very difficult to work in workbook using drawing instruments. It is well known fact that, any drawing is prepared on suitable standard size of drawing sheets only. The instructor is herewith advised to go through the instructions given below and to follow them in view of imparting much drawing skill in the trainees. Acquiring the above said ability and doing small drawings is not a simple task. These books will provide a good platform for achieving the said skills.
Time allotment: Duration of 1st Year : 80 Hrs
Time allotment for each module has been given below. Common to all 1 year and 2 year Engineering Trades.
S.No Title Exercise No. Time allotment
1 Engineering Drawing Introduction 1.1.01 - 1.1.04 1 2 Drawing Instrument 1.2.05 - 1.2.07 1 3 Free hand drawing 1.3.08 - 1.3.14 10 4 Lines 1.4.15 & 1.4.16 2 5 Drawing of Geometrical figures 1.5.17 - 1.5.21 8 6 Lettering & Numbering 1.6.22 6 7 Dimensioning and its Practice 1.7.23 - 1.7.25 4 8 Sizes and layout of drawing sheets 1.8.26 2 9 Method of presentation of Engineering Drawing 1.9.27 & 1.9.28 2 10 Symbolic representation – different symbols used in the trades 1.10.29 - 1.10.33 6 11 Projections 1.11.34 - 1.11.37 15 12 Orthographic projection from isometric projection 1.12.38 15 13 Reading of fabrication drawing 1.13.39 8 80 Hrs Instructions to the Instructors It is suggested to get the drawing prepared on A4/A3 sheets preferably on only one side. If separate table and chair facility is available for every trainee then it is preferred to use A3 sheets and if the drawing hall is provided with desks then A4 sheets may be used. However while preparing bigger drawings on A4 sheets suitable reduction scale to be used or muiltiple sheets may be used for detailed and assembly drawings. First the border and the title block to be drawn only for the first sheet of the chapter. Eg. for conical sections only first sheet will have the title block whereas the rest of the sheets of that chapter will have only borders. Serial number of sheet and total no. of sheets to be mentioned on each sheet. The completed sheet to be punched and filled in a box file/ suitable files and preserved by the trainees carefully after the approval of instructors, VPS and Principals of the Institute. The file may be reffered by the authority before granting the internal marks at the end of 1st year.
(vi) Copyright Free. Under CC BY License. CONTENTS
Exercise No. Title of the Exercise Page No.
Engineering Drawing Introduction
1.1.01 Introduction to engineering drawing 1 1.1.02 Conventions 4 1.1.03 Views of engineering drawing sheets 5 1.1.04 Method of folding of printed drawing sheets as per BIS SP: 46-2003 7
Drawing Instrument
1.2.05 Drawing instruments - Drawing board, T - square, drafter (drafting machine) 9 1.2.06 Drawing instruments - Setsquares, protractor and scale 11 1.2.07 Drawing Instruments box and pencils 12
Free hand drawing
1.3.08 Free hand drawing of lines 15 1.3.09 Free hand drawing - Polygons and ellipse 20 1.3.10 Free hand drawing of geometrical figures and block with dimension 24 1.3.11 Free hand drawing of transferring measurement from the given object 25 1.3.12 Free hand drawing of solid figures, cubes, cuboids, cone, prism, pyramid, frustum of cone with dimensions 29 1.3.13 Freehand drawing of hand tools and measuring tools used in common trades 32 1.3.14 Freehand drawing of simple fasteners (bolts, nuts and rivets etc.) trade related sketches 49
Lines
1.4.15 Lines - Definition, types and applications in drawing as per BIS: 46-2003 and classification of lines 51 1.4.16 Lines - Drawing lines of given length (straight, curved), drawing of parallel lines, perpendicular line and methods of division of line segment 55
Drawing of Geometrical figures
1.5.17 Drawing of geometrical figures - Definition, nomenclature and practice of angle, measurement and its types, and types of angle and triangle 59 1.5.18 Drawing of geometrical figures - Method of bisecting practice of angles and triangles 61 1.5.19 Geometrical figures - Square, rectangle, rhombus, parallelogram, circle and its elements 66 1.5.20 Drawing of geometrical figures - Practice of square, rectangle, parallelogram, rhombus and circle 68 1.5.21 Drawing of geometrical figures - Different polygons and their values of included angles. Inscribed and circumscribed polygons 74
Lettering & Numbering
1.6.22 Lettering and numbering - Single stroke, double stroke and inclined 77
(vii) Copyright Free. Under CC BY License. Exercise No. Title of the Exercise Page No.
Dimensioning and its Practice
1.7.23 Dimensioning - Definition, and its types, types of arrow heads and leaderline with text 85 1.7.24 Dimensioning and its practice - Methods of dimensions and position of dimensioning (aligned, unidirectional) 87 1.7.25 Symbols preceding the value of dimension and dimensional tolerance 97
Sizes and layout of drawing sheets
1.8.26 Sizes and layout of drawing sheets - Selection of sizes, title Block, its position & content and item reference on drawing sheet (item list) 100
Method of presentation of Engineering Drawing
1.9.27 Method of presentation of engineering drawing - Pictorial view and isometric view 104 1.9.28 Method of presentation of engineering drawing - Orthographic views 114
Symbolic representation – different symbols used in the trades
1.10.29 Symbolic representation - different symbols used in the trades - Fastener (bolts, nuts and rivets) 116 1.10.30 Symbolic representation of bars and profile sections 119 1.10.31 Symbolic representation of weld, brazed and soldered joints 120 1.10.32 Symbolic representation of electrical and electronic elements 122 1.10.33 Symbolic representation of piping joints and fittings 126
Projections
1.11.34 Projections - Concept of axes plane and quadrant 128 1.11.35 Projections - Orthographic projection 131 1.11.36 Projection - Method of 1st angle and 3rd angle projections (Deifinition and difference) 136 1.11.37 Projection - Symbol of 1st angle and 3rd angle projection as per IS specification 138 Orthographic projection from isometric projection 1.12.38 Drawing of orthographic projection from isometric projection 139 Reading of fabrication drawing 1.13.39 Reading of fabrication drawing for sheet metal worker trade 143
LEARNING / ASSESSABLE OUTCOME
On completion of this book you shall be able to
• Read and apply engineering drawing for different application in the field of work.
(viii) Copyright Free. Under CC BY License. SYLLABUS
1st Year Common for all Engineering trades under CTS Duration: One Year (Not applicable for Draughtsman trade Group)
S.no. Syllabus Time in Hrs
I Engineering Drawing – Introduction 1
Introduction to Engineering Drawing and Drawing Instruments – 1 Conventions 2 Viewing of engineering drawing sheets. 3 Method of Folding of printed Drawing sheet as per BIS SP: 46-2003
II Drawing Instrument 1
1 Drawing board, T-square, Drafter (Drafting M/c), Set squares, Protector, Drawing Instrument Box (Compass, Dividers, Scale, Diagonal Scales etc.), pencils of different grades, Drawing pins/ Clips.
III Free hand drawing of – 10
1 Lines, polygons, ellipse etc. 2 Geometrical figures and blocks with dimension 3 Transferring measurement from the given object to the free hand sketches. 4 Solid objects - Cube, Cuboids, Cone, Prism, Pyramid, Frustum of Cone with dimensions. 5 Free hand drawing of hand tools and measuring tools, simple fasteners (nuts, bolts, rivets etc.) trade related sketches
IV Lines 2
1 Definition, types and applications in drawing as per BIS: 46-2003 2 Classification of lines (Hidden, centre, construction, extension, Dimension, Section) 3 Drawing lines of given length (Straight, curved) 4 Drawing of parallel lines, perpendicular line 5 Methods of Division of line segment
V Drawing of Geometrical figures: 8
Definition, nomenclature and practice of – 1 Angle: Measurement and its types, method of bisecting. 2 Triangle: different types 3 Rectangle, Square, Rhombus, Parallelogram. 4 Circle and its elements 5 Different polygon and their values of included angles. Inscribed and circumscribed polygons
(ix) Copyright Free. Under CC BY License. S.no. Syllabus Time in Hrs
VI Lettering & Numbering 6
1 Single Stroke, Double Stroke, Inclined.
VII Dimensioning and its Practice 4
1 Definition, types and methods of dimensioning (functional, non-functional and auxiliary) 2 Position of dimensioning (Unidirectional, Aligned) 3 Types of arrowhead 4 Leader line with text 5 Symbols preceding the value of dimension and dimensional tolerance.
VIII Sizes and layout of drawing sheets 2
1 Selection of sizes 2 Title Block, its position and content 3 Item Reference on Drawing Sheet (Item list)
IX Method of presentation of Engineering Drawing 2
1 Pictorial View 2 Orthographic View 3 Isometric View
X Symbolic representation – different symbols used in the trades 6
1 Fastener (Rivets, Bolts and Nuts) 2 Bars and profile sections 3 Weld, Brazed and soldered joints 4 Electrical and electronics element 5 Piping joints and fitting
XI Projections 15
1 Concept of axes plane and quadrant 2 Orthographic projections 3 Method of first angle and third angle projections (definition and difference) 4 Symbol of 1st angle and 3rd angle projection.
XII Orthographic projection from isometric projection 15
XIII Reading of fabrication drawing 8
Total 80
(x) Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.1.01 Engineering Drawing Introduction to engineering drawing
Communication Limitations of graphical language There are many different ways of communicating ideas, 1 Information /feelings can be conveyed effectively but informations, instructions, requests, etc. They can be still there are chances for imagination (communication transmitted by signs or gestures, by word of mouth, in gap). writing, or graphically. In an industrial context the graphical method is commonly used, communication being achieved 2 Viewer may image anything in his mind due to the by means of engineering drawings. absence of written language. If oral and written communication only were used when Limitations of vocal language dealing with technical matters, misunderstandings could 1 Speaker and the listener should be aware of same arise, particularly in relation to shape and size. The lack language. of a universal spoken language makes communication and understanding even more difficult because of the necessity 2 Still there are chances of misunderstanding due to to translate both words and meaning from one language communication gap. to another. 3 Some languages (without alphabets) are existing on However, the universally accepted methods used in tongues only. graphical communication through engineering drawings 4 Written language can also be misunderstood as each eliminate many of these difficulties and make it possible and every word gives more than one meaning. for drawing prepared by a British designer to be correctly interpreted or “read” by, for example, his German, French Limitations of computer language ot Dutch counterpart. 1 Used only by computer programmers. Equally important, the components shown on the drawings 2 Cannot be used for general communication. could be made by suitably skilled craftsmen of any nationality provided they can “read” an engineering drawing. Conclusion Conventionally prepared engineering drawing provide the Effective communication is possible when graphical main means of communication between the “ideas” men language is supported by written language/vocal language (the designers and draughtsman) and the craftsmen and vice versa. (machinists, fitters, assemblers, etc.). For the Engineering drawing is a language which uses both communication to be effective, everyone concerned must graphical language and written language for effective interpret the drawing in the same way. Only then will the communication finished product be exactly as the designer envisages it. Eg. In FM radios jockeys use vocal language To ensure uniformity of interpretation the British Standards Eg. News papers use graphical language + Written Institution have prepared a booklet entitled BS 308:1972, language Engineering Drawing Practice. Now in three parts, this publication recommends the methods which should be Eg. In television they use Graphical language (motion/ adopted for the preparation of drawing used in the still pictures) + written language + vocal language engineering industry. For Effective communication The standards and conventions in most common use and hence those required for a basic understanding of Engineering drawing is a graphical language Engineering Drawing are illustrated and explained in this which also uses written language for effective book. communication Limitations of sign language Importance of Engineering Drawing 1 Information/feelings cannot be conveyed effectively The economical success of any country is mainly depended on its industrial development. Due to the 2 Chances of misunderstanding the information / feelings globalization any industry of our country expected to be of 3 Both the communicator and the receiver to be present global market standard. Due to the above said reason our at the same place Indian product required to be of very high quality with respect to size of dimension, fit, tolerance and finish etc.
1 Copyright Free. Under CC BY License. To produce a best standard product all the technical Technical drawings personnel (Engineers to Craftsman) in an industry must Technical drawings allows efficient communication among have a sound knowledge in engineering drawing because engineers and can be kept as a record of the planning engineering drawing is the language of engineers. process. Since a picture is worth a thousand words, a Engineering drawing is a universal language. Different types technical drawing is a much more effective tool for of lines are its alphabets. Technical personnel in any engineers than a written plan. industry including craftsmen are expected to communicate anything concerning a part or a component by drawings The technical drawing, on the other hand is not subtle, or involving lines, symbols, convention and abbreviations etc. abstract. It does not require an understanding of its creator, only on understanding of technical drawings. A technical With our spoken languages it is impossible to express drawing is a means of clearly and concisely communicating the details of a job or a product. Engineering drawing all of the information necessary to transform an idea or a knowledge and practice are must for designing or producing concept in to reality. Therefore, a technical drawing often a component or part. Even a small mistake in the drawing contains more than just a graphic representation of its may reflect very badly in the product. Therefore reading subject. It also contains dimensions, notes and and doing engineering drawing are very much essential for specifications. craftsmen and engineers Fields of use: A drawing is a graphical representation of an object, or part of it, and is the result of creative thought by an engineer Technical drawing is the preferred method of drafting in all or technician. When one person sketches a rough map in engineering fields, including, but not limited to, civil giving direction to another, this is graphic communication. engineering, electrical engineering, mechanical engineering Graphic communication involves using visual materials to and architecture. relate ideas. Drawings, photographs, slides, Purpose of studying engineering drawing: transparencies, and sketches are all forms of graphic communication. Any medium that uses a graphic image 1 To develop the ability to produce simple engineering to aid in conveying a message, instructions, or an idea is drawing and sketches based on current practice involved in graphic communication. 2 To develop the skills to read manufacturing and One of the most widely used forms of graphic construction drawings used in industry. communication is the drawing. Technically, it can be 3 To develop a working knowledge of the layout of plant defined as "a graphic representation of an idea, a and equipment. concept or an entity which actually or potentially exists in life" 4 To develop skills in abstracting information from calculation sheets and schematic diagrams to produce Drawing is one of the oldest forms of communicating, working drawings for manufacturers, installers and dating back even farther than verbal communication. The fabricators. drawing itself is a way communicating necessary information about an abstract, such as an idea or concept Main types of Engineering drawing: or a graphic representation of some real entity, such as a Regardless of branch of engineering the engineering drawing machine part, house or tools. There are two basic types is used. However based on the major engineering of drawings: Artistic and Technical drawings. branches, engineering drawing can be classified as follows: (Fig 1)
2 Engineering Drawing : (NSQF) Exercise 1.1.01 Copyright Free. Under CC BY License. Mechanical engineering drawings: Some examples of mechanical engineering drawings are part and assembly drawings, riveted joints, welded joints, fabrication drawings, pneumatics and hydraulics drawings, pipeline diagrams, keys coupling drawings etc. (Fig 2)
Electrical Engineering drawings Wiring diagrams of home and industries, circuit diagrams, electrical installation drawings etc. Example The voltage supply to a filament lamp is 10.8V. The voltage should be 12V. (Fig 4)
Audio amplifier (Fig 5)
Answer the following questions. 1 Discuss the different types of drawings? 2 Explain the different applications of technical drawing? 3 What is graphical communications?
Engineering Drawing : (NSQF) Exercise 1.1.01 3 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.1.02 Engineering Drawing
Conventions
TYPE CONVENTION MATERIALS
Steel, Cast Iron, Copper and its Alloys,
Aluminium and its alloy, etc
Metals
Lead, Zinc Tin White-metal, etc.
Glass Glass
Porcelain, Stoneware, Marble, Slate etc
Packing and Insulating Asbestos, Fibre, Felt, Synthetic resin, materials Products, Paper, Cork, Linoleum, Rubber, Leather, Wax, insulating & Filling Materials etc
Liquid Water, Oil, Petrol, Kerosene etc
Wood Wood, Plywood etc
Concrete Concrete
4 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.1.03 Engineering Drawing
Views of engineering drawing sheets
Drawing paper: These are of two types: TABLE 1 • Hand-made paper Designation Trimmed size Untrimmed size • Mill-made paper A0 841 x 1189 880 x 1230 Hand-made papers have rough surfaces, pale in colour and A1 594 x 841 625 x 880 not used for regular work, but meant for charts. A2 420 x 594 450 x 625 Mill-made papers are most commonly used for regular A3 297 x 420 330 x 450 work, and are available in different sizes and rolls. They are A4 210 x 297 240 x 330 specified by their weight in kg per ream or density in grams A5 148 x 210 165 x 240 per square meter. Size of drawing sheets (in mm): While working or For drawings which cannot be accommodated in above handling, the papers are liable to tear on the edges. So sheets, elongated series are used. Elongated series are slightly large size (untrimmed) sheets are preferred. They designated by symbols A1 x 3; A2 x 4 etc. are trimmed afterwards. IS:10811:1983 lays down such as Special elongated series increasing its widths, double, designation of preferred trimmed and untrimmed sizes. treble etc. are designated as follows A3 x 3, A3 x 4, A4 x The basic principle involved in arriving at the sizes of the 3, A4 x 4, A4 x 5. Please refer Table 2 drawing paper is as under. The area of the biggest size (A0) TABLE 2 is 1m2 and its breadth and length are in the ratio . Let 2:1 Special elongated series x and y are the sides of the paper. The surface area of A0 Designation Size is 1m2, then the sides are x = 0.841 m and y = 1.189 m. (Fig1) A3 x 3 420 x 891 A3 x 4 420 x 1189 A4 x 3 297 x 630 A4 x 4 297 x 841 A4 x 5 297 x 1051
Exceptional elongated series Designation Size
A0 x 2 1189 x 1682 A0 x 3 1189 x 2523 A1 x 3 841 x 1783 A1 x 4 841 x 2378 Two series of successive sizes are obtained by either halving or doubling along the length. The area of the A2 x 3 594 x 1261 successive sizes are in the ratio of 1:2. A2 x 4 594 x 1682 Designation of sheets: The drawing sheets are designated A2 x 5 594 x 2102 by symbols such as A0, A1, A2, A3, A4 and A5. A0 being A3 x 5 420 x 1486 the largest. Table 1 below gives the length and breadth of A3 x 6 420 x 1783 the above sizes of sheets. (Trimmed and untrimmed) A3 x 7 420 x 2080 The relationship between two sides is same as that of a A4 x 6 297 x 1261 side of a square and its diagonal. A4 x 7 297 x 1471 A4 x 8 297 x 1682 A4 x 9 297 x 1892
5 Copyright Free. Under CC BY License. A4 x 3 means the length of A4 size is retained and the other side is 3 times the width of A4. A4 x 3 = 297 x 630 (210 x 3) Fig 2 & 3 shows how the sheet sizes are formed by halving/ doubling and similarity of format.
Quality drawing paper: The drawing papers should have sufficient teeth or grain to take the pencil lines and withstand repeated erasing. A backing paper is to be placed on the drawing board before White drawing papers which do not become yellow on fixing drawing/tracing paper, to get uniform lines. Before exposure to atmosphere are used for finished drawings, starting the drawing, the layout should be drawn. (Ref: maps, charts and drawings for photographic reproductions. IS:10711) For pencil layouts and working drawings, cream colour papers are best suited.
6 Engineering Drawing : (NSQF) Exercise 1.1.03 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.1.04 Engineering Drawing
Method of folding of printed drawing sheets as per BIS SP: 46-2003
Method of folding of printed drawing sheets as per When the drawings are to be released to shop floor for BIS SP: 46-2003 reference during manufacturing of a component When drawings sheets are in more numbers, they have to Applicability be folded and kept in order to save the trace required for preserving them (Fig 1). Folding of drawings applies to only the drawings which are released for shop floor for manufacturing of components / reference. Original drawings will never be taken out of drawing office and they should be kept under safe custody. Drawings which are prepared on tracing sheets/ transparencies like cloth, polymer, acrylic polymer transparencies should never be folded. They should be kept in polythene folders and kept in filing cabinets. Sometimes the blue prints/photo copies of drawings which are released to shop floor are also laminated for extending their life. Requirement While folding the drawings following care to be taken. It is required to fold the drawings such that, they should not get defaced damaged. Drawing sheet to be folded such that the title block is easily visible to retrieve it and keeping it back.
7 Copyright Free. Under CC BY License. The following is the method of folding printed drawing sheets as recommended by BIS (Fig 2)
8 Engineering Drawing : (NSQF) Exercise 1.1.04 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.2.05 Engineering Drawing
Drawing instruments - Drawing board, T - square, drafter (drafting machine)
The following are the commonly used equipment in a drawing office. Sl. No. Designation Blade length Drawing board (Fig 1): Drawing board is one of the main 1 T0 1500 equipment of Draughtsman. It is used for supporting the drawing paper/tracing paper for making drawings. It is 2 T1 1000 made of well seasoned wood strips of about 25 mm thick 3 T2 700 or masonite, free from knots and warping. It should be 4 T3 500 softer enough to allow insertion and removal of drawing pins. Two battens are fastened to the board by screws, in The ‘T’ square is used with its head against the ebony edge slotted joints. They prevent warping and at the same time of the drawing board to draw horizontal lines, parallel lines permit expansion and contraction of the strips due to the and to guide/hold the setsquares, stencils etc. change of moisture in the atmosphere. Fig 2b shows how the ‘T’ square is used. ‘T’ square should never be used as a hammer or as guide for trimming papers
One of the shorter edges of the drawing board, is provided with an “ebony edge” (hard wood) fitted perfectly straight. Standard drawing boards are designated as follows as per IS:1444-1989.
Sl. No. Designation Size (mm)
1 D0 1500 x 1000 x 25 2 D1 1000 x 700 x 25 3 D2 00 x 500 x 15 4 D3 500 x 350 x 15
The working edge (ebony) must be straight. Now-a-days the drawing boards are available with laminated surfaces. The flatness can be checked by placing a straight edge on its surface. If no light passes between Drafting in the machine (Fig 3): It serves the functions of them, the surface is perfectly flat. a Tee square, set square, protractor and scale. They come in different sizes and a pattern called ‘Pantagraph’ type. It ‘T’ Square: It is of ‘T’ shape, made of well seasoned wood. is fitted on the top left side, edge of the drafting board, It has two parts., head and blade. One of the edge of the mounted on an adjustable frame or table. It requires large blade is the working edge. The blade is screwed to this area of working place. The angle of the drafting board can head such that the working edge is at right angle to head. be adjusted by pedal operating system. There are two (Fig 2a) counter weights to balance the angular position of the The standard ‘T’ square are designated as follows with board and the drafting head. It is more suitable for production dimensions shown in mm; as per IS:1360-1989. drawing office.
9 Copyright Free. Under CC BY License. On the other end, a protractor head H with swivelling and locking arrangement is fitted with two scales at right angles. The protractor head has a spring loaded clutch relieving handle, which rotates and locks at 150 intervals automatically. For setting any angle other than multiples of 150, the clutch spring is released and by rotating the centre knob, the zero line is set to the required angle and the friction clutch knob is tightened. It is capable of rotating 1800, thereby any angle can be set. The scales are bevelled on both sides, graduates to 1:1 & Erasing shield: When, on a drawing, if a part of a line or 1:2., They can be reversed with the help of dovetail slide some lines among many other lines need to be erased or fitting. modified, in normal way of erasing will damage the other There is a fine adjusting mechanism on the drafting head nearby lines. In such a situation an erasing shield is to set the scale parallel to the edge of the board. The scales effectively useful. It is a thin metallic sheet having small also can be adjusted if there is any error in measuring 900 openings of different sizes and shapes. A suitable opening between them. is aligned to the line to be erased and the line is removed Mini drafter is an important device used for making drawing by the eraser. (Fig 7) quickly& accurately. This instrument has the combination of T-square, setsquare, protractor and scales, it helps to draw the drawings at a faster rate. (Fig 4,5 & 6)
10 Engineering Drawing : (NSQF) Exercise 1.2.05 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.2.06 Engineering Drawing
Drawing instruments - Setsquares, protractor and scale Set square (IS:1361-1988): Transparent celluloid /Plastic The angles can be set or measured from both sides, setsquares are preferred and are commonly used rather aligning the reference line and point ‘0’ with the corner point ebonite ones. They are two in number, each having one of the angle. corner with 90°. The setsquare with 60°-30° of 250 mm long Figure 3 shows how to read or set the angle. Protractor can and 45° of 200mm long is convenient for use. Setsquares also be used to divide a circle or drawing sectors. sometimes loose their accuracy due to internal strains. So they should be tested periodically. (Fig 1)
French curves These are made in many different shapes, normally come in sets of 6,12,16 etc. French curves are best suited to draw smooth curves/ arcs (which cannot be drawn by a compass) with ease. To draw a smooth curve using french curve first Sometimes set squares have french curves. Set squares set it by trial against a part of the line to be drawn, then shift are used to draw all straight lines except horizontal lines. it to the next portions. It is convenient to draw horizontal lines using Mini drafter. Each new portion should fit atleast three points on the curve With the help of Mini drafter and manipulating the 45°, 30°- just drawn. It should be seen that the curve (radius) is 60° setsquares, angular lines in the multiples of 15°; increasing or decreasing smoothly and no corner should be Parallel lines to a given inclined line and perpendicular to formed on the curve(Fig 4). can be drawn. Set squares with graduated, bevel edge and french curve openings are preferable. They are also used to draw smooth curves. Setsquare should never be used as guide for trimming papers. Scales: Scales are used to transfer and or to measure the dimensions. They are made of wood, steel, ivory, celluloid or plastic, stainless steel scales are more durable. different types of scales used are shown in Figs 1,2 & 3. They are either flat, bevel edged or triangular cross-section. Scales of 15cm long, 2cm wide or 30cm long 3.5cm wide flat scales are in general use. Thin section or bevel edged scales are preferred over thick flat scales. Parallax error will Fig 5 show how to use the french curve and draw a smooth be nil or least while using thin / tapered edge scales. (Fig2) curves. They are made of transparent celluloid (no bevel edge).
Protractor: Protractor is an instrument for measuring angles. It is semi-circular or circular in shapes and is made of flat celluloid sheet.
11 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.2.07 Engineering Drawing
Drawing Instruments box and pencils
The quality of a good drawing does not only depend on the talent of the craftsmen but also on the quality of instruments he uses. Drawing instruments are generally sold in sets in boxes, but they are also available separately. The main parts of high grade instruments are generally made of nickel or brass. They must be rust proof. Tool steel is used for making the blades of the inking pen, bow instruments and various screws. An instrument box contains the following: (Fig 1a to h) • Large compass (with attachment facility) (a) • large divider (b) • Bow compasses, bow divider (c) • Lengthening bar (d) • Pen point for attachment (e) • Screw driver (f) • Lead case (g) • Liner (h) Large compass (Fig 2) : It has a knee joint in one leg that permits the insertion of pen or pencil point or attaching lengthening bar with pen or pencil point attached to it. It is used for drawing large circles/arcs also for taking large measurements. The pin on the other leg can be swivelled to vertical position when drawing large circles, while drawing the circles of arcs it should be held in such a way that the needle point leg and pencil point leg should be bent so as to make perpendicular to the paper.
As a rule while drawing concentric circles, small circles should be drawn first before the centre hole gets worn.
Large divider: It is used to transfer dimensions and dividing lines into a number of equal parts. Divider with adjustable joints is preferable rather than plain legs. (Fig 3)
12 Copyright Free. Under CC BY License. Bow instruments: Bow pencil and bow pen compass are Inking pen or liner or ruling pen (Fig 6): It is used to ink used for drawing circles of approximately 25 mm radius. the straight lines drawn with the instruments but never for Bow divider is used for marking or dividing smaller spaces. free hand lines or lettering. There are two types (i) Integral legs with spring action (4e) (ii) two legs held with a curved spring on top with handle on it. Bow instruments may have adjusting wheel and nut. To draw circles, it is better to mark the required distance separately and set the instruments and check. Then only the circles or arcs should be drawn on the drawing. Fig 4 shows different types of bow instruments. Adjustment should be made with the thumb and middle finger. The Lengthening bar (Fig 7): To draw larger circles, it is fitted instrument is manipulated by twisting the knurled head to the compass. The pencil point or pen point is inserted between the thumb and finger. to its end.
Replaceable spare pencil, pen and needle points for compass are available in the instrument box. Screw driver (Fig 8): Used for adjusting the screws of the instruments.
Lead case (Fig 9): Lead case is the box for holding the pencil leads.
Drop spring bow pencil and pen (Fig 5): Drop spring bow pencil and pen are designed for drawing multiple identical small circles. Example: rivet holes, drilled/reamed holes. The central pin is made to move freely up and down through the tube attached to the pen or pencil unit. It is used by Pin, Clip, Cello tape: Drawing sheet should be fastened holding the knurled head of the tube between thumb and on to the drawing board firmly on temporary basis so that middle finger while the index finger is placed on the top of it does not shake during preparing drawing. For this the pin. The pin point is placed on the centre point of the purpose the pins, clips and cello tapes are used (Fig 10) circle to be drawn (Fig 5) and pencil or pen is lowered until it touches paper. The instrument is turned clockwise and the circle is drawn.
Pencils, Grade and Selection Pencils (Fig 11): In drawing office, standard pencils (lead encased in wood) and semi-automatic pencils are made use. Pencil leads are made of graphite with kaolin (clay) of varying proportion to get the desired grades. More the kaolin higher the hardness. Grades of pencils: Pencils are graded according to the hardness or softness of the lead.
Engineering Drawing : (NSQF) Exercise 1.2.07 13 Copyright Free. Under CC BY License. In summer the pencil leads become softer due to rise in temperature, so slightly harder pencils can be made use of softer grade pencils are used on smooth surfaces for lettering and arrow head. During rainy season or when humidity is more, the drawing paper expands and wrinkles form, pencil leads become harder. So softer pencils are to be used. Whatever may be grade of pencil you use, always prefer quality pencils/leads viz., Venus, Kohinoor, Apsara etc. For better line work, i.e., dense black lines, prefer paper which is not having too much teeth (roughness). Selection of pencils: Pencil grades vary from one brand to another brand. Select the grades of the pencil depending Hardest pencil is 9H grade and softest pencil is 7B upon the type of line work. For construction lines, you can grade. Selection of grade of pencils depends on the type choose 2H or 3H, for lettering and object lines grade H of line work required and paper on which it is used. pencils. In general H, HB and 2H are used. Softer lead pencils are used to produce thicker and darker H medium hard line work, but they wear out quickly. Medium grade of H, HB medium soft 2H are used for general line work as well as for lettering. 2H hard Harder grade leads produce lighter and thinner lines. Most Pencils used for drawing are always hexagonal in cross construction line work is done with 4H, 5H and 6H pencil sections as they do not roll easily even when they are leads, producing thin but also sufficiently dark by exerting placed on slope surfaces. Its cross section helps in pressure. Depending upon the individuals touch and the rotating the pencil, while drawing lines, to give uniform line style of writing, right pencil may be selected. thickness. For any drawing on drawing paper or tracing paper, lines Now-a-days automatic (Mechanical) pencils or clutch should be black, particularly drawings which are to be pencils are available in different sizes (lead dia 0.3, 0.5, 0.7 reproduced. For this purpose, the pencil chosen must be or 0.9 mm). They are easy to handle as there is no soft enough to produce jet black lines as well hard enough reduction of holding length pencil leads can be replaced, as not to smudge easily. The point should not crumble under per required grade of hardness. They produce lines of normal working pressure. The pencils should not be hard uniform width without sharpening. (Fig 11) and cut grooves on the p0aper while drawing with normal pressure, Pencils H, 2H or 3H depending upon the paper (quality) and weather conditions are selected.
14 Engineering Drawing : (NSQF) Exercise 1.2.07 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.3.08 Engineering Drawing
Free hand drawing of lines
Sketch by free hand 2 To draw vertical lines in thick and thin. (Fig 2) Follow the procedure and sketch the following practice • Sketch two horizontal thin guide lines AB & CD. No.1 to 17 in A3/A4 sheets. • Mark points on the horizontal lines AB & CD, 5 mm Practice intervals. 1 To draw horizontal thick and thin lines. (Fig 1) • Sketch the line in free hand between the two points with • Sketch two vertical thin guide lines AB & CD. thick and thin alternatively. • Mark points on the vertical lines AB & CD, 5 mm intervals approximately. Vertical lines are drawn from top to bottom. (Fig 2B) • Draw the lines by free hand between the two points sketch thick and thin alternatively. Lengthy lines can be drawn with the forearm motion and short lines are drawn with the wrist motion. Keep uniform pressure while sketching. Horizontal lines are drawn from left to right. (Fig 1B) While sketching straight lines between two points keep your eyes on the point to which the line is to go rather than the point of pencil. Avoid of drawing whole length of line in one single stroke. Prevent using eraser often.
3 Sketch the inclined lines as shown in figure with thick and thin lines. (Fig 3) • Sketch two axis AB & CD. • On the horizontal and vertical axis AB and CD, mark points with 5 mm intervals. • Draw thick and thin lines in the direction as shown in the figure alternatively.
15 Copyright Free. Under CC BY License. Inclined lines running upward are drawn left to right i.e bottom to top. (Fig 3B) The pencil point need not to be too sharp. Hold the pencil freely and not close to the point. It is better that the pencil can be hold 30 mm away from the tip of the pencil lead.
5 Sketch the plane figure as shown. (Fig 5) • Sketch a square box of 30 mm side in thin lines. • Mark off the dimensions as shown in figure approximately. • Thick the required lines. • Erase the unwanted lines and complete the figure.
6 Sketch the plane figure as given. (Fig 6) • Form a square box of 30 mm side in thin lines. • Set of the dimensions and angle as shown in figure. • Draw the lines and remove the unwanted lines. • Complete the figure.
4 Sketch the given plane figure as shown. (Fig 4) • Draw the horizontal straight line in free hand and mark off 60 mm approximately. • Draw a vertical straight line of 60 mm long from the base. • Draw horizontal & vertical parallel lines and form a square box of 60 mm sides. • Darken the lines of the surfaces in figure using thick line. • Erase the unwanted lines and complete the plane figure. 7 Sketch a circle of diameter 50 mm. (Fig 7) Do not place any dimensions in the figure. • Sketch a square box of given diameter, mark the mid points and join the mid points of horizontal and vertical sides. (Fig 7A) • Join the corners (diagonals) of the square box and mark the radius of the given diameter. (Fig 7B) 16 Engineering Drawing : (NSQF) Exercise 1.3.08 Copyright Free. Under CC BY License. • Join all the 8 points by a smooth curve and complete the • Sketch a rectangular box of 85 mm x 60 mm. circle. (Fig 7C) • Mark of the dimensions as shown in figure. • Erase the unwanted lines and darken the curve. (Fig 7D) • Follow the method given in Ex.7,8 and sketch the circle. Side of the square = Diameter of the circle • Thick the required lines. Radius of circle = Half of the square side. • Erase the unwanted lines and complete the figure.
10 Sketch the blank shown in figure. (Fig 10) • Sketch a rectangular box of 75 mm x 60 mm as is figure. • Mark the other dimensions as shown in figure. • Thick the required lines of the template. • Erase the unwanted lines and complete the figure.
8 Sketch the template as shown in figure. (Fig 8) • Sketch a square box of 60 mm side. • Sketch the semi-circle on right side of the square as shown in figure. • Darken the lines as in figure and complete the shape of 11 Sketch the curved shape blank plane figure as the template. given in figure. (Fig 11) • Draw a vertical straight line and horizontal straight line intersecting each other at right angles. • Mark off 20 mm on either side of the vertical line from the intersecting point of the straight lines. • Sketch semi-circle of R 20 mm top and bottom as in figure. • Join the two semi-circles with vertical lines. • Sketch the three circles of 10 mm. • Darken the lines and complete the figure.
9 Sketch the given figure. (Fig 9)
Engineering Drawing : (NSQF) Exercise 1.3.08 17 Copyright Free. Under CC BY License. 12 Sketch the template as shown. (Fig 12) • Darken the squares as per exercise drawing. • Draw a vertical straight line. • Rub off the thin construction lines and complete the exercise. • Draw two horizontal straight lines intersecting the vertical line keeping 40 mm away. • Sketch the two curves as in figure and join the curves. • Erase the unwanted lines and complete the figure.
15 Draw the pattern of sides 70 mm and 35 mm by free hand proportional to the size. (Fig 15) • Draw a rectangle proportionately. • Join the diagonals. • Draw parallel lines to the diagonals approximately at 10 mm distance from each other as shown in the exercise.
13 To sketch an ellipse of given major and minor axis. (Fig 13) • Draw a horizontal and a vertical line intersecting each other at right angles. • On the horizontal line mark the half of the major axis on either side of the centre and similarly half of the minor axis on the vertical line. • Through these points draw horizontal and vertical parallel lines and form a rectangular box. 16 Draw a square ABCD of side 80 mm approximately by free hand. (Fig 16) • Sketch the small arcs with thin lines. • Join diagonals (thin line). • Join the other portion by smooth curve and complete the ellipse. • Draw the perpendicular bisectors from two adjacent sides (free hand). • On side AB, mark EF = 20 mm. • Join E and F to centre of square. • Draw a line at a distance 10 mm parallel to EF. • The parallel line cuts the inclined lines EO and FO at G and H. • Join GH, GE and HF. • Follow the procedure and draw trapeziums similar to EFHG on the remaining three sides. • Join the lines shown in the Fig 16 and rub off the thin line and finish the drawing.
14 Draw the pattern of 50 mm side by free hand. (Fig14) • Draw a square by free hand. • Divide one horizontal and one vertical side into each ten equal parts. • Draw a thin horizontal and vertical line through the parts marked.
18 Engineering Drawing : (NSQF) Exercise 1.3.08 Copyright Free. Under CC BY License. 17 Sketch the given pattern by free hand. (Fig 17) • Mark the mid point of the line AB. • Draw free hand circles of 35 and 50 on the mid point of the vertical line. • Draw two circles 20 mm using A and B are the centres. • Draw two circles of 10 from points A and B. • Complete the drawing after removing unwanted lines. Vertical line (Fig 21a): Lines which are perpendicular to Plane figures for which the procedure are not horizontal lines are called vertical lines. It can be treated as given follow the constructional methods given a line along the plumb line of the plumb bob or parallel to in Skill sequences and the Procedures for a plumb line. (Fig 21b) plane figures and complete them.
Inclined line or Oblique line: A straight line which is neither horizontal nor vertical is called an inclined line. Types of lines (Fig22) A point represents a location in space, having no width or height. It is represented by drawing intersection of lines or a dot. (Fig 18)
Curved line: It is the path of a point which always change its direction. Examples of curved lines are shown in (Fig23).
Line is the path of a point when it moves. It has no thickness and are of two types: • Straight line Parallel lines: They are the lines with same distance between them. They may be straight lines or curved line • Curved line Parallel lines do not meet when extended. (Fig 24) Straight line: It is the path of a point when it is moving in a particular direction. It has only length and no width.(Fig19) Also a straight line is the shortest distance between two points. Straight line, depending on its orientation are classified as Horizontal, Vertical and Inclined or Oblique line. Perpendicular lines: When two lines meet at 90°,the two lines are said to be perpendicular to each other. One of the lines is called as reference line. (Fig 25)
Horizontal line (Fig 19): Horizontal lines are those which are parallel to a horizontal plane. Example of horizontal plane is the surface of a still water. (Fig 20)
Engineering Drawing : (NSQF) Exercise 1.3.08 19 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.3.09 Engineering Drawing
Free hand drawing - Polygons and ellipse
Names of polygons: Polygons are named in terms of their S.No Name No. of sides number of sides as given below: (Fig 1) 1 Pentagon – a Five sides 2 Hexagon – b Six sides 3 Heptagon – c Seven sides 4 Octagon – d Eight sides 5 Nonagon – e Nine sides 6 Decagon – f Ten sides 7 Undecagon – g Eleven sides 8 Duodecagon – h Twelve sides
• Pentagon inscribed polygon. (Fig 2) • Pentagon circumscribed polygon. (Fig 3)
- O as centre and OF as radius describe a circle of dia 50 mm. - Draw the line DF vertically beyond the top of the circle.
20 Copyright Free. Under CC BY License. - Divide the circle into 10 equal parts. (Twice as many • Hexagon regular heptagon (Fig 8) equal parts as the number of sides) - Points 1,3,5,7 and 9 are the tangent points of the pentagon. - Join 02, 04, 06, 08, 010 and extend to a convenient length. - Draw a tangent to the circle through point 1 (F). Hexagon • The sum of the interior angle and the corresponding external angle is 180°. (Fig 4)
• Semi-circular method heptagon (Fig 9)
• Hexagon arc method (Fig 5)
• Hexagon arc method (Fig 6) • Hexagon perpendicular bisector method. (Fig 10)
• Hexagon across flats method (Fig 7)
• Special method octagon (Fig 11)
Engineering Drawing : (NSQF) Exercise 1.3.09 21 Copyright Free. Under CC BY License. Freehand drawing of ellipse
Elements of an ellipse (Fig 1) • String and pins method • Paper trammel method • 4 centre method • Conjugate diameters method • Eccentricity method Practical applications: In general, a circle in a pictorial drawing is represented by an ellipse. The use of elliptical shape is rarely used for engineering applications. Ellipse is dealt extensively in mathematical books. Elliptical shape is adopted for better aesthetics. 1 Construct an ellipse by concentric circle method. Major axis: It is the longest distance which passes Major axis 80 mm. Minor axis 40 mm. (Fig 2) through the centre, at right angle to the fixed lines called the directrix. AB is the major axis. Minor axis: It is the maximum distance which bisects the major axis at right angle. It will be parallel to the directrix. CD is the minor axis. Directrix: It is a straight line perpendicular to the major axis. Focus: When an arc is drawn with C or D as centre and radius equal to half the major axis i.e , it is cut at two points F1 and F2 on the major axis. F1 and F2 are the focal points of an ellipse F1 or F2 is the focus. The sum of the distances from F1, F2 to any point on the curve i.e., F1P +
F2P is always constant and equal to the major axis. • Draw the major axis AB (80 mm) and minor axis CD Focal radii: The distances from point P on the curve to the (40 mm), bisecting at right angle at 0. focal points F1 and F2 are called focal radii. Sum of the focal radii is equal to the major axis. • '0' as centre OA and OC as radius, draw two concentric circles. Eccentricity: The ratio between the distances from the vertex to focus and vertex to the directrix is called the • Draw a number of radial lines through '0' (say 12) eccentricity and is always less than one. cutting the two circles.
AF1/A0 is less than one. • Mark the points on the outer circle as a,b,c. It can also be stated as the ratio of the distance from focus • Similarly mark the corresponding intersecting points onto any point on the curve, say P1 and the perpendicular on inner circle as a',b',c'. distance of P from the directrix. i.e P F /P M is a 1 1 1 1 • From points such as a,b,c... draw lines parallel to constant. minor axis. Vertex: The end points of the major axis on the curve are • From points such as a', b',c'.... draw lines parallel to called vertex. (A, B) the major axis to intersect with the corresponding
Tangent and normal to an ellipse: Normal is the line vertical lines at points P1, P2,P3.... etc. bisecting the angle F PF in Fig 1. Tangent in a line at 90° 1 2 • Join all these points with a smooth curve by free to the normal and touching the ellipse. hand or using "french curve" and form the ellipse. Directrix, axis, focus, vertex and tangent are the elements • To find the 'Foci' - with half the major axis (a) as common to ellipse, parabola and hyperbola. radius and with 'C' on the minor axis as centre, draw All ellipse can be constructed in different methods: an arc cutting the major axis, at two points, mark them as F F the focus points of the ellipse. • Rectangle method (oblong) 1 2 2 Construct an ellipse by four centre method - Major axis • Concentric circle method = 80 mm and Minor axis = 40 mm - Type A. (Fig 3) • Arcs method
22 Engineering Drawing : (NSQF) Exercise 1.3.09 Copyright Free. Under CC BY License. • Draw the major axis A1A2 and minor axis B1B2.
• Set off B1M2 and B2M4 equals to A1B1.
• Join A1B1 and set off B1B3 equal to a-b (a = OA1, b
= OB1) • Join DP meeting EC at K.
• Draw a bisector on A1B3 which intersects A1A2 at • Draw perpendicular bisectors of KD and extend DC
M1. and locate point `S'.
• Similarly obtain M3. M2 & M4 as centres and B1M2 • 'S' as centre SD as radius draw the arc KD. as radius, draw arcs P P & P P . 1 2 3 4 • Similarly get the point 'R'. •MM as centres and M P as radius, draw arcs P P 1 3 1 1 1 3 • Join AK and draw perpendicular bisector on it, and & P2P4 and complete the ellipse. meet AB at f1. 3 Construct an ellipse by four centre method - Major axis •'f' as centre, Af as radius, draw an arc KK'. = 80 mm and Minor axis = 40 mm - Type B. (Fig 4) 1 1 • Mark centre 'f ' so that Bf = Af . • Draw the rectangle EFGH (80 x 40) and draw AB & 2 2 1 CD represent major and minor axis. • Now R, S, F1 & F2 are the four centres of the ellipse. • Join EC Similar to the procedure followed for drawing curves KD and KK and complete the ellipse • Bisect AE and mark P the mid-point. 1
Engineering Drawing : (NSQF) Exercise 1.3.09 23 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.3.10 Engineering Drawing
Free hand drawing of geometrical figures and block with dimension Free hand sketching: Apart from making drawing using Materials for free hand sketching: A4 size sheet instruments, often craftsman will be required to make (preferably a pad instead of loose papers) pencils of soft drawings by free hand. grade. Example H, HB, and a good quality eraser are the Free hand sketching is an easiest method to express the only materials required. For drawing different darkness, shape of a piece part or a component by an engineer or the pencil points should be sharpened to conical shape. craftsman. Here are a few examples of situation wherein free hand sketches will have to be necessarily made. • On the site sketching for production/maintenance. • Recording of initial idea of a design. • For quick exchange of ideas among designer, draughtsman, technician. • Urgency (free hand sketching takes less time) To make free hand drawings/sketches, the craftsman has to acquire new skills and one has to have considerable practice to be able to make good free hand sketches. Ability to make good free hand sketches is an asset to any craftsman. Free hand sketches are not usually made to scale. However, they should be as nearly to the proportions as possible. Rectangular block (Fig 4) Cube (Fig 2)
Square block (Fig 5) Square block (Fig 3)
Cylinder (Fig 6)
24 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.3.11 Engineering Drawing
Free hand drawing of transferring measurement from the given object
25 Copyright Free. Under CC BY License. 26 Engineering Drawing : (NSQF) Exercise 1.3.11 Copyright Free. Under CC BY License. Transfer all the dimensions from the figures 1 to 10 of page nos.25 & 26 to the given objects below
Engineering Drawing : (NSQF) Exercise 1.3.11 27 Copyright Free. Under CC BY License. 28 Engineering Drawing : (NSQF) Exercise 1.3.11 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.3.12 Engineering Drawing
Free hand drawing of solid figures, cubes, cuboids, cone, prism, pyramid, frustum of cone with dimensions
Cube (Fig 1) • Similarly draw two more lines parallel to AB and AE mark G interesting point from F and C. • Draw lines parallel to DC and FG Draw lines parallel to DF and GC. • Join all the points. Cylinder (Fig 3)
• Draw square of a, b, c and d. • Draw 300 lines from point b, c and d for the length of 25mm. • Mark point g from b, f from c and e from d as shown in figure. • Joint all points. Rectangular prism (Fig 4) Cuboid (Fig 2)
Square Prism (Fig 5)
Draw the isometric drawing of a cuboid of base 30 mm x 40 mm and the height 20 mm. (Fig 2) Drawthe three isometric axes through point ‘A’. • Mark AB = 40mm, AE = 30mm and AD= 20mm representing the three sides of cuboid. • Draw two vertical lines parallel to the line EF and BC from point E and B respectively.
29 Copyright Free. Under CC BY License. Triangular Prism (Fig 6) base. All the slant triangular faces join at a common point called APEX. Similar to prisms, pyramids also are known by the shape of their base viz triangular, square, rectangular, pentagonal, hexagonal etc. The imaginary line joining the centre of the base to the apex is called the AXIS. Fig 10 shows some pyramids and their views.
Pentagonal prism (Fig 7)
Hexagonal prism (Fig 8) When a semi-circle revolves about its diameter a sphere is generated. A sphere has no flat surface. (Fig 11D)
Cone: When a right angled triangle revolves about one of its side forming the right angle, a cone is generated. Cone The term solids of revolution is a mathematical concept and forming has a circular face and a slant curved surface. a physical requirement in geometry. (Fig9) Frustums: Pyramid/cone is cut parallel to the base and the top portion is removed. The remaining bottom portion is called frustum of a pyramid/cone. If the cutting plane is at an angle to the axis/base, of the pyramids or cone they are called "Truncated pyramids or cones". Fig 12&13 shows frustums and truncated pyramids. All items we use are solids. Their shapes may confirm to individual geometrical solids like prisms, cones or other combination. Figure 13 shows some items. Pyramids: Pyramids are polyhedron solids having a base Draw the isometric view of a cone whose base diameter 40 surface whose shape may be triangular, square or polygon mm and height 60 mm when its base rest on horizontal and as many slant triangular faces as there are sides in the plain surface. (Fig 14) 30 Engineering Drawing : (NSQF) Exercise 1.3.12 Copyright Free. Under CC BY License. • From ‘0’ draw tangents to the isometric circle of the base and complete the required isometric view of the cone. (Fig 14c) Draw the isometric views of a hexagonal pyramid of side base 30 mm and height 75 mm given its position as under: • Its base resting on HP and the edge of the base parallel to VP. (Fig 15)
• Draw the front view and top view of the cone in the true scale as shown in the Fig 14a.
• Draw the top view and front view of the pyramid (true scale) and enclose the top view in the rectangle PQRS. (Fig 15a) • Draw the parallelogram with two of its adjacent edges at 300 to the horizontal. (Fig 15b) PQ = Isometric length of pq and PS = Isometric length of PS. • Draw an isometric hexagon ABCDEF in the parallelogram PQRS. (Fig 15b)
• Draw the isometric view of the base circle, (by four • Mark the centre ‘O’ and draw a vertical line from point centre method) (Fig 14b) ‘O’ of height to 75 mm in isometric scale. • Join ‘O’ with ABCDE&F to complete the required • Mark the centre and draw vertical line 0.01 such that 0.01 equals to 60 mm in isometric scale. isometric projection of the hexagonal pyramid. (Fig15c) Engineering Drawing : (NSQF) Exercise 1.3.12 31 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.3.13 Engineering Drawing
Freehand drawing of hand tools and measuring tools used in common trades
Hand Tools Files (Fig 1) Hacksaw (Fig 6) a Curved cut file b Rasp cut file c Single cut file d Double cut file
Ball pein hammer (Fig 7)
Scriber (Fig 2)
Chisel (Fig 8)
Divider (Fig 3) ‘C’ clamp (Fig 9)
Outside caliper (Fig 4)
Screw driver (Fig 10)
Inside caliper (Fig 5)
32 Copyright Free. Under CC BY License. Bench vice (Fig 11) Hammers (Fig 16)
Measuring Tools Steel rule (Fig 17)
Centre punch (Fig 12)
Try square (Fig 18)
Cutting plier (Fig 13) Vernier caliper (Fig 19)
Open end spanner (Fig 14) Micrometer (Fig 20)
Marking gauge (Fig 15) Vernier height gauge (Fig 21)
Engineering Drawing : (NSQF) Exercise 1.3.13 33 Copyright Free. Under CC BY License. Feeler gauge (Fig 22) Combination set (Fig 26)
Bevel protractor (Fig 23)
Vernier depth gauge (Fig 27)
Slip gauge box (Fig 24)
Depth micrometer (Fig 28)
Sine bar with dial gauge (Fig 25)
34 Engineering Drawing : (NSQF) Exercise 1.3.13 Copyright Free. Under CC BY License. Freehand drawing of hand tools and measuring tools used in electrician, electronics mechanic and wireman trades
Screw driver (Fig 1) Instrument screw driver (Fig 4)
Screw driver interchangeable tips (Fig 5)
Screw driver with cross type tips (Fig 2)
Special type screw driver (two rectangular recesses) (Fig6) Screw tips aided screw heads (Fig 3)
Engineering Drawing : (NSQF) Exercise 1.3.13 35 Copyright Free. Under CC BY License. Special type screw driver (two round recesses) (Fig 7) Melted solder blocking flux cores (Fig 10)
Pliers (Fig 8) Soldering iron (Fig 11)
Ratchet brace (Fig 12)
Analog multimeter (Fig 9)
Neon Tester (Fig 13)
36 Engineering Drawing : (NSQF) Exercise 1.3.13 Copyright Free. Under CC BY License. Gimlet (Fig 14) Electric drilling machine (Fig 18)
Bradawl & poker (Fig 15)
Hand drill (Fig 19)
Electrician’s knife (Fig 16)
Mallet (Fig 17)
Rawl plug tool (Fig 20)
Engineering Drawing : (NSQF) Exercise 1.3.13 37 Copyright Free. Under CC BY License. Freehand drawing of hand tools and measuring tools used in mechanic motor vehicle and mechanic diesel trades
Spanners (Fig 1) Adjustable spanner (Fig 3)
Socket spanner (Fig 4)
Sliding ‘T’ handle socket spanner (Fig 2)
38 Engineering Drawing : (NSQF) Exercise 1.3.13 Copyright Free. Under CC BY License. Pliers (Fig 5) Socket extension bars (Fig 7)
Round nose plier (Fig 8)
Stillson pipe wrench (Fig 9) Cutting plier (Fig 6)
Pipe cutter (Fig 10)
Engineering Drawing : (NSQF) Exercise 1.3.13 39 Copyright Free. Under CC BY License. Puller (Fig 11) Piston ring expander (Fig 14)
Testing valve spring tension (Fig 15)
Valve spring compressor & valve grinder (Fig 12)
Connecting rod alignment fixture (Fig 16)
Wooden block & ring compressor (Fig 13)
40 Engineering Drawing : (NSQF) Exercise 1.3.13 Copyright Free. Under CC BY License. Freehand drawing of hand tools and measuring tools used in plumber trade
Face wrench (Fig 1) Mortar pan (Fig 5)
Bricklaying trowel (Fig 6) Hook wrench (Fig 2)
Jointing board (Fig 7) Spade (Fig 3)
Steel square (Fig 8) Pickaxe (Fig 4)
Engineering Drawing : (NSQF) Exercise 1.3.13 41 Copyright Free. Under CC BY License. Spirit levels (Fig 9) Chain pipe vice (Fig 14)
Line and pins (Fig 10)
Pipe cutter (Fig 15)
Square and bevel (Fig 11)
Multi wheel chain pipe cutter (Fig 16)
Gin wheel (Fig 12)
Accurate tube bender (Fig 17)
Pipe vice (Fig 13)
Pinch-off tool (Fig 18)
42 Engineering Drawing : (NSQF) Exercise 1.3.13 Copyright Free. Under CC BY License. Freehand drawing of hand tools and measuring tools used in welder trade
Electrode holder (Fig 1) A.C welding transformer (Fig 5)
Earth clamp (Fig 2)
Cable attachments (Fig 6)
Work cable attachments (Fig 3)
Cutting torch (Fig 7)
Goggles (Fig 4) Regulator (Fig 8)
Engineering Drawing : (NSQF) Exercise 1.3.13 43 Copyright Free. Under CC BY License. Freehand drawing of hand tools and measuring tools used in carpenter trade
Collapsible carpenter rule (Fig 1) Try square (Fig 5)
Plumb bob (Fig 6) Folding rule (Fig 2)
Crow bar (Fig 7)
Tape Measure (Fig 3)
Carpenter’s work bench (Fig 4) Marking knife or striking knife (Fig 8)
44 Engineering Drawing : (NSQF) Exercise 1.3.13 Copyright Free. Under CC BY License. Marking knife (Fig 9) Coping saw (Fig 14)
‘T’ - Bevels (or) bevel square (Fig 10) Fret saw (Fig 15)
Compass saw (Fig 16) Standard wire gauge (Fig 11)
Bow saw (Fig 17)
Panel gauge (Fig 12)
Steel scriber (Fig 18)
Cross cut saw (Fig 13)
Engineering Drawing : (NSQF) Exercise 1.3.13 45 Copyright Free. Under CC BY License. Butt gauge (Fig 19) Pairs of pincers (Fig 20)
Marking gauge (Fig 21)
Freehand drawing of hand tools and measuring tools used in foundryman trade
Trowels (Fig 1) Cleaner or lifter (Fig 2)
Rammers (Fig 3 & 4)
46 Engineering Drawing : (NSQF) Exercise 1.3.13 Copyright Free. Under CC BY License. Spirit level (Fig 9)
Vent wire (Fig 5)
Hand bellow (Fig 10)
Draw spike (Fig 6 & 7) Foundry brush (Fig 11)
Mallets (Fig 12)
Leveler (Fig 8)
Engineering Drawing : (NSQF) Exercise 1.3.13 47 Copyright Free. Under CC BY License. Swab (Fig 13) Riddle (Fig 16)
Water sprinkler (Fig 17) Hand shovel (Fig 14)
Runner and riser pins (Fig 15)
Smoothers (Fig 18)
48 Engineering Drawing : (NSQF) Exercise 1.3.13 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.3.14 Engineering Drawing
Freehand drawing of simple fasteners (bolts, nuts and rivets etc.) trade related sketches Hexagonal headed bolt (Fig 1) Square nuts (Fig 5)
Square headed bolt (Fig 2)
Hexagonal nuts (Fig 3 & 4) Dome nut and cap nut (Fig 6)
Collared nut (Fig 7)
49 Copyright Free. Under CC BY License. Types of rivets (Fig 8)
50 Engineering Drawing : (NSQF) Exercise 1.3.14 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.4.15 Engineering Drawing
Lines - Definition, types and applications in drawing as per BIS: 46-2003 and classification of lines
Drawings are made up of different types of lines. Just as Technical drawings are drawn with different types of lines. language with alphabets and grammar. By proper choice and application of lines product features can be correctly defined in a drawing. Different types of Lines of different thickness and features are used for lines recommended for specific applications are given in specific use (Fig 1 and 2). Table 1. Table 1 Types of lines and their application Lines Description General applications See figure and other relevant figure
Continuous thick A1 Visible outlines A2 Visible edges Continuous thin B1 Imaginary lines of intersection (straight) B2 Dimension lines B3 projection lines or extension line B4 Leader lines B5 Hatching B6 Outlines of revolved sections in place B7 Short centre lines B8 Thread line B9 Diagonal line Continuous thin C1 Limits of partial or interrupted views & free hand sections, if the limit is not a chain thin Continuous thin D1 Line (See figures) (Straight) with zig-zags
Dashed thick E1 Hidden outlines E2 Hidden edges Dashed thin F1 Hidden outlines F2 Hidden edges Chain thin G1 Centre lines G2 Lines of symmetry G3 Trajectories Chain thin, thick at ends H1 Cutting planes & changes of direction
Chain thick J1 Indication of lines or surfaces to which a special requirement applies Chain thin double- K1 Outlines of adjacent parts dashed K2 Alternative and extreme positions of movable parts K3 Centroidal lines K4 Initial outlines prior to forming K5 Parts situated in front of the cutting plane 1 This type of line is suited for production of drawings by machines. 2 Although two alternatives are available, it is recommended that on any one drawing, only one type of line be used.
Thickness of the line should be chosen according to the In the above range, for craftsman 0.5 is preferred. The Table size and type of the drawing from the following range. 2 shows the 0.5 line range and other lines under this range. (IS:10714-1983) 0.18, 0.25, 0.35, 0.5, 0.7, 1, 1.4 & 2 mm. The numbers in right side of the lines refers the line thickness in mm. 51 Copyright Free. Under CC BY License. Table 2 – without a dot or arrow head (Fig 5)
Hatching lines (B5): Hatching lines are the lines inclined parallel lines. The minimum space between these lines should be more than twice the thickness of the heaviest line in the drawing. It is recommended that these spacings should never be less than 0.7 mm. (Fig 4) For showing the limits of partial or interrupted views and sections continuous thin free hand lines (C1) or continuous thin straight lines with zig-zag (D1) are used. (Fig 6)
All the views of a component drawn to one particular scale should have the same range of line thickness. Types of lines: Ten types of lines are used in general engineering drawing as per IS:10714-1983. Out of which first four types of lines are continues lines of both thick and thin. (Type A to D) Continuous thick line (A type) is used for drawing visible outlines (A1) and visible edges (A2). (Fig 3) These lines are also called as object lines.
Lines of type E to K in Table 1 are of the non-continuous type. Some of these thin and some are thick. For hidden lines both thick and thin dashes (E & F type) are available, it is recommended that on any one drawing, only one type of (Thick or thin) line be used. (Fig 7)
Continuous thin lines (B type): Continues thin lines are used for many applications as stated in Table 1. A few applications of B types of lines are shown in Fig 4.
Chain lines (Thin): Chain lines are used for drawing centre lines of circles, cylinders etc. Same lines are also used to show the axis of symmetry in symmetrical objects. To save time and space a partial of a whole component is drawn. The line of symmetry is identified at its ends by two thin short parallel lines drawn at right angle to it. (Fig 8) Another method of representing symmetrical shape is to extend the object lines beyond the axis of the symmetry. (Fig 9) In this case the short parallel lines described above A leader line - B4 (Fig 4): A leader line is a line referring is omitted. The same lines are also used to show the to a feature (dimension, object, outline etc). A leader line repetitions of features of a component. (Fig 10) should terminate For drawing a sectional view, plane of cutting is to be shown – with a dot in other view. Cutting plane (H1) in Table 1 is drawn with thin chain, thick at ends and also at the places of direction – with an arrow head change. (Figs 11 & 12)
52 Engineering Drawing : (NSQF) Exercise 1.4.15 Copyright Free. Under CC BY License. If thick chain lines (J1) in table 1 are drawn on a surface, it indicates some special treatment/application on that surface. (Fig 13) Chain thin double dashed (K) lines are applied for the following: K1 - Outlines of adjacent parts (Fig 13) K2 - Alternative and extreme positions of moving parts. (Fig 13)
K3 - Centroidal lines (Fig 14)
Engineering Drawing : (NSQF) Exercise 1.4.15 53 Copyright Free. Under CC BY License. K4 - Initial outlines prior to forming (Fig 13)
K5 - Parts situated in front of the cutting plane (Fig14)
54 Engineering Drawing : (NSQF) Exercise 1.4.15 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.4.16 Engineering Drawing
Lines - Drawing lines of given length (straight, curved), drawing of parallel lines, perpendicular line and methods of division of line segment
There are a lot of ways to define straight and curved lines; the most elaborate way to define them is the following: • A straight line is a succession of points that are aligned in the same direction. Or in other words, in order to go from one point to another, we never change direction.
• On the contrary, the points of a curved line do change direction from one point to the next. Tangent line
• If there aren’t any obstacles, there are plenty of ways to do this…for example: 4 Easy ways to draw curved line
Drawing curved dashed line
To join two lines, that are at right angles, with a given radius The accompanying figures show four steps for how to draw a right angled joint. • Draw a right angle and arcs that represents the desired radius. (Fig 11a)
55 Copyright Free. Under CC BY License. • Draw tangential lines on these arcs. (Fig 11b) • Place the compass point on CP and draw the radius which starts at BP and ends at EP. (Fig 11c) • Join CP with BP and EP with perpendicular lines. (Fig11c) • Join the radius with straight lines. (Fig 11d)
The accompanying figures show four steps of how to draw • Join CP with BP and EP with perpendicular lines. an acute joint. (Fig12c) • Draw an acute angle with arcs that represents the • Place the compass point on CP and draw the radius desired radius. (Fig 12a) which starts at BP and ends at EP. (Fig 12c) • Draw tangential lines on these arcs. (Fig 12b) • Join the radius with straight lines. (Fig 12d)
Follow the procedure and draw the exercise in the A3/A4 2 Draw six vertical parallel lines of 50 mm length sheet. with 10 mm intervals (Fig 2). Procedure 1 Draw six horizontal parallel lines of 50 mm long with 10 mm intervals (Fig 1).
• Draw a vertical line AB 50 mm long, using setsquare on left side. • Draw a horizontal line AB 50 mm long. • Mark points on the vertical line AB with 10 mm intervals. • Mark the points with 10 mm intervals. • Butt a setsquare on the line AB. • Butt a setsquare on the line AB. • Using another setsquare, draw parallel lines through • Using another setsquare draw vertical parallel lines the points marked. from left to right. Use sharpened conical point pencil. Draw the vertical lines from bottom to top. Keep the pencil slightly inclined towards the direction of the movement. 3 Draw 45° inclined lines (Fig 3). While drawing rotate the pencil to keep the • Draw a horizontal line AB 60 mm long. constant thickness. • Butt a setsquare on the line AB, draw vertical lines from Maintain uniform pressure on the lead of the the points A and B using another setsquare. pencil. • Set off AD and BC equals to 40 mm and complete the box.
56 Engineering Drawing : (NSQF) Exercise 1.4.16 Copyright Free. Under CC BY License. • On lines AB and DC mark 10 mm points. • Butting the 60° setsquare on the line AB, using 45° setsquare draw inclined parallel lines through the marked points.
Draw lines from bottom to top.
2 Draw the following exercises on A4 sheets (Fig 4).
4
EDN141624
Engineering Drawing : (NSQF) Exercise 1.4.16 57 Copyright Free. Under CC BY License. Division of a line segment • Let CB = x, then AC = 2x Before knowing about the division of a Line segment, let us • AC + CB = 2x + x = 15, x = 5 know what a line and line segment means, • AC = 10 cm and CB = 5 cm. Line and line segment • Mark point C, 10 cm away from A A line is a collection of points along a straight path which extends to both the directions without endpoints. (Fig 5)
AB is a line which doesn’t have any ending. (Fig 6)
A line segment is a part of a line between two endpoints. PQ is a line segment having P and Q as end points on the Method of division of line segments line AB. Division of a line segment A line segment can be divided into ‘n’ equal parts, where ‘n’ is any natural number. For example; a line segment of length 10 cm is divided into two equal parts by using a ruler as, • Mark a point 5 cm away from one end. • 10 cm is divided into two 5 cm line segments. Similarly, a line segment of length 15 cm can be divided in the ratio 2:1 as, • AB is the line segment of length 15 cm and C divides the line in the ratio 2:1.
58 Engineering Drawing : (NSQF) Exercise 1.4.16 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.5.17 Engineering Drawing
Drawing of geometrical figures - Definition, nomenclature and practice of angle - Measurement and its types, and types of angle and triangle
Angles: Angle is the inclination between two straight lines meeting at a point or meet when extended. AB and BC are two straight lines meeting at B. The inclination between them is called an angle. The angle is expressed in degrees or radians.
Concept of a degree: When the circumference of a circle Reflex angle: It is the angle which is more than 180o. is divided into 360 equal parts and radial lines are drawn (Fig6) through these points, the inclination between the two adjacent radial lines is defined as one degree. Thus a circle is said to contain 360o. (Fig 1)
Adjacent angles: These are the angles lying on either side of a line. (Fig 7)
Acute angle: If an angle which is less than 90o is called an acute angle. (Fig 2)
Complementary angles: When the sum of the two angles is equal to 90o, angle POQ + angle QOR = 90o angle POQ and angle QOR are complementary angles to each other. (Fig 8) Right angle: Angle between a reference line and a perpendicular line is called right angle. (Fig 3)
Obtuse angle: This refer to an angle between 90o and Supplementary angle: When the sum of the two adjacent 180o. (Fig 4) angles is equal to 180o, example angle SOT + angle TOY = 180o, angle SOT and angle TOY are supplementary angles to each other. (Fig 9)
Straight angle: This refers to an angle of 180o. This is also called as the angle of a straight line. (Fig 5)
59 Copyright Free. Under CC BY License. Triangle - different types
Triangle is a closed plane figure having three sides and 4 Right angled triangle is one in which one of the three angles. The sum of the three angles always equals angles is equal to 90° (Right angle). The side opposite to 180°. to right angle is called hypotenuse. (Fig 4) To define a triangle, we need to have a minimum of three measurements as follows: • 3 sides or • 2 sides and one angle or • 2 angles and one side Types of triangles 1 Equilateral triangle is a triangle having all the three sides equal. Also all the three angles are equal (60°) (Fig 1) 5 Acute angled triangle is one in which all the three angles are less than 90°. (Fig 5)
2 Isosceles triangle has two of its sides equal. The angles opposite to the two equal sides are also equal. 6 Obtuse angled triangle has one of the angles more (Fig 2) than 90°. (Fig 6)
3 Scalene triangle has all the three sides unequal in lengths. All the three angles are also unequal. (Fig 3) The sum of the three angles in any triangle is equal to 180°. The sum of any two sides is more than the third side.
60 Engineering Drawing : (NSQF) Exercise 1.5.17 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.5.18 Engineering Drawing
Drawing of geometrical figures - Method of bisecting practice of angles and triangles
Procedure • `E' as centre AE as radius draw an arc to cut the 1 Bisect a given straight line (Fig 1). previous arc at `C'. • Draw a line AB of 70 mm long. • `C' as centre and with the same radius draw another arc to cut at `D'. • With A and B as centres, more than half of AB as radius describe arcs on either side of the line AB. • C and D as centre with the same radius draw arcs on top side which intersect at ‘O’. • Let the arcs intersect at C & D. • Join OA and AO is perpendicular to the line AB from the • Join CD, bisecting the line AB at 0. point `A'. • CD is the bisector of the line AB and AO = OB.
4 Draw a line parallel to a given line at a given distance (Fig 4). • Draw a line AB to a convenient length (say 60 mm). • Draw a line CD (40 mm) is the given distance. • Mark points 1 & 2 near A & B respectively. 2 Draw a perpendicular to a given straight line, from a given point in it (Fig 2). • With 1 & 2 as centres CD as radius draw arcs. • `C' is the point on the line AB. • At 1 & 2 errect perpendiculars by using setsquares, meeting at E & F respectively. • `C' as centre draw arcs on the line AB at 1 & 2. • Join the points E & F. • 1 and 2 are centres draw arcs. The arcs intersect at D. • EF is parallel to AB at the given distance of CD. • Join DC. • CD is the perpendicular line from the point `C'.
5 Divide a line into any number of equal parts (Fig5). 3 Draw a perpendicular to a given straight line when the point is at the end of the line (Fig 3) • Draw a line AB to a convenient length (say 65 mm). • Draw a line AB (say 75 mm). • At `A' draw a line AC to a required length, forming an angle BAC. (Always it is better to form an acute angle) • `A' as centre to a convenient radius draw an arc to meet AB at E. 61 Copyright Free. Under CC BY License. • Set off 5 equal arcs on the line AC meeting at 1,2,3,4 • D and E as centre with the same radius draw arcs which & 5. (As many equal parts as required) intersect at point ‘O’. • Join 5 & B. • Join AO. • From the points 4,3,2 & 1 draw lines parallel to 5-B • AO is the bisector of the angle BAC. meeting the line AB at 4', 3', 2' & 1'. • Now OAB OAC . • Now the line AB is divided into 5 equal parts. 8 Construct an angle equal to 75° (Fig 8). • Draw a line BC (60 mm long).
• At `B' erect a perpendicular GB and now GBC is a right angle. • Trisect the angle FBC at D & E. • Bisect the angle FBD at `A'.
6 Trisect a given right angle (Fig 6). • Now angle ABC = 75°. • Draw a right angle ABC. • With `B' as centre to convenient radius, draw an arc meeting the line BC and BA at 1 & 2 respectively. • With 1 & 2 as centres, B-1 as radius draw arcs to cut the previous arc at D & E respectively. • Join BE & BD. • Now .
1 9 Construct an angle equal to 22 (Fig 9). 2 • Draw a line BC to a convenient length. • At `B' erect a perpendicular BD and DBC is right angle. • Bisect the DBC at `E'. 45 EBC DBE EBC 45 • Bisect EBC at `A'. 1 • Now BCA = 22 . 2 7 Bisect a given angle (Fig 7).
• Construct an angle BAC (say 30°). • `A' as centre to a convenient radius draw an arc to cut line AC at `E' and AB at `D'.
62 Engineering Drawing : (NSQF) Exercise 1.5.18 Copyright Free. Under CC BY License. Triangles
Procedure 4 Scalene triangle: AB = 30 mm, AC = 55 mm & BC= 1 Equilateral triangle (Fig 1) AB = BC = CA = 35 mm. 35 mm. • Draw a line and mark AB 35 mm the side of triangle. • Draw base AB = 30. • With radius AB and center A and B, draw arcs cutting • `A' as centre draw an arc of radius 55. at C (Fig 1). • `B' as centre draw an arc of 35 cutting the previous arc • Join CA and CB. at `C'. • ABC is a required triangle. • Join CA and CB. AB = 30, BC = 35 and AC = 55 ABC is the required triangle. (Fig 4)
2 Isosceles triangle : AB = AC = 40 mm & BAC 40 . • Draw the side AB equal to 40 mm. `A' as centre, draw an arc of radius AB. • Draw a line AC at 40° to AB. • Join BC to form the triangle ABC. (Fig 2) 5 Scalene triangle: AB = 40 mm, AC = 30 mm & 30 BCA 30 . • Draw base AB (40 mm) and a perpendicular from its mid point. • Set/draw the given angle 30° such that angle BAD = 30° (Angle C). • Erect perpendicular to AD at `A'. • Extend both perpendiculars to meet at `O'. • AO as radius and `O' as centre, draw a circle or an arc. • Side AC (30 mm) as radius and `A' as centre, draw an 3 Isosceles triangle (Fig 3): Altitude = 40 mm & arc cutting the previous arc at `C'. 65 BAC BCA BAC 65 • Join CA and CB. ABC is the required triangle. (Fig 5)
• Draw any line X'Y' and erect a perpendicular DB of height 40 mm at a convenient point `D'. • Draw a parallel line XY to X'Y' through `B'. • Draw A'B at 65° to XY and extend to meet at `A' on the line X'Y'. • Locate another point C on line X'Y' same way as in the previous step and complete the triangle ABC.
Engineering Drawing : (NSQF) Exercise 1.5.18 63 Copyright Free. Under CC BY License. 6 Scalene triangle: AB = 70 mm Follow the above said procedure and construct the exercises 110 BAC & 40 ABC 40 & BAC 110 from 15 to 19. • Draw line AB = 70 15 Draw a triangle when one side and 2 angles being given (Fig 8). • Set 110° at `A' using protractor. • Set angle B = 40° using protractor. Extend the line meeting at `C'. Join `C' with A and B. ABC is the required triangle. (Fig 6)
7 Right angled triangle: AB = 60 mm, BC = 45 mm • Draw the horizontal line BC to length 45 mm. • Erect a perpendicular to length 60 mm at `B'. 16 Draw a right angled triangle when the base and • Join AC. hypotenuse being given (Fig 9). ABC is the required triangle. (Fig 7)
Construct triangles as per the procedure with given dimensions. 8 Draw an equilateral triangle ABC of sides 35 mm. 9 Draw an isosceles triangle ABC in which sides AB and 17 Draw a triangle the altitude and two sides being given (Fig 10). AC are equal to 40 mm and BAC is equal to 40°. 10 Draw an isosceles triangle ABC in which the altitude BD = 40 mm and BAC and BCA = 65°. 11 Draw a scalene triangle ABC in which the side AB =30 mm; AC = 55 mm and BC = 35 mm. 12 Draw a scalene triangle ABC in which the side AB =40; AC = 30 and the angle BCA = 30°. 13 Draw a scalene triangle ABC in which the side AB =30 mm; ABC = 40° and BAC = 110°. 14 Draw a right angled triangle ABC in which the sides AB and BC are 60 and 45 mm respectively.
64 Engineering Drawing : (NSQF) Exercise 1.5.18 Copyright Free. Under CC BY License. 18 Draw a triangle the base, altitude and vertical angle 19 Draw a triangle the base, altitude and one side being being given (Fig 11). given (Fig 12).
Engineering Drawing : (NSQF) Exercise 1.5.18 65 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.5.19 Engineering Drawing
Geometrical figures - Square, rectangle, rhombus, parallelogram, circle and its elements
Quadrilateral is a plane figure bounded by four sides and four angles. Sum of the four angles in a quadrilateral is (interior angles) equal to 360°. The side joining opposite corners is called diagonal. To construct a quadrilateral out of four sides, four angles and two diagonals a minimum of five dimensions are required of which two must be sides. Quadrilaterals are also referred as Trapezium. (Fig 1)
Angle ABC = Angle ADC and Angle BAD = Angle BCD. Diagonals AC and BD are not equal but bisecting at right angles.
AO = OC and BO = OD.
To construct a rhombus we need to know (a) two diagonals (b) one diagonal and an opposite angle or (c) one side and its adjacent angle. Types of quadrilaterals (Fig 1) Rhomboid/Parallelogram (Fig 4): In a parallelogram • Square opposite sides are equal and parallel. Opposite angles are • Rectangle also equal. Diagonals are not equal but bisect each other. • Rhombus • Rhomboid / Parallelogram Square: In a square all the four sides are equal and its four angles are at right angles. The two diagonals are equal and perpendicular to each other. To construct a square we need to know (a) length of the side or (b) length of the diagonal. Rectangle (Fig 2): In a rectangle, opposite sides are equal and parallel and all four angles are right angles. Parallelogram is also known as rhomboid. To construct a parallelogram we need (a) two adjacent sides and an angle between them or (b) one side, diagonal, and an angle between them or (c) two adjacent sides and perpendicular distance between the opposite sides.
In the parallelogram ABCD, AB = DC; AD = BC
To construct a rectangle we need to know the length (a) two Angle DAB = angle DCB, angle ABC = angle ADC adjacent sides or (b) diagonal and one side. Sides AB,CD and AD, BC are parallel. Fig 2 shows a rectangle ABCD, Sides AB = DC and BC = AD. Diagonals AC and BD are equal. Diagonals are not Diagonals AC and BD are not equal but bisect at 0. bisect at right angles. Rhombus (Fig 3): In rhombus all the four sides are equal but only the opposite angles are equal. ABCD is the rhombus where AB = BC = CD = AD.
66 Copyright Free. Under CC BY License. Circles, Tangents
Circle: Circle is a plane figure bounded by a curve, formed by the locus of a point which moves so that it is always at a fixed distance from a stationery point the "Centre". Radius: The distance from the centre to any point on the circle is called the "Radius". Diameter: The length of a straight line between two points on the curve, passing through the centre is called the "Diameter". (D: Dia or d) It is twice the radius. Circumference: It is the linear length of the entire curve, equal to D . Arc: A part of the circle between any two points on the circumference or periphery is called an 'Arc'. Chord: A straight line joining the ends of an arc is called the chord. (Longest chord of the circle is the diameter) Segment: A part of the circle or area bound by the arc and chord is the segment of the circle. Sector: It is the part of a circle bounded by two radii (plural of radius) meeting at an angle and an arc. Quadrant: Part of a circle with radii making 90o with each other is a quadrant (one fourth of the circle). Half of the circle is called as semi-circle. Eccentric circles: Circles within a circle but with different centres are called eccentric circles. (Fig 3) Tangent: Tangent of a circle is a straight line just touching the circle at a point. It does not cut or pass through the circle when extended. The point where the tangent touches the circle is called the "point of tangency". The angle between the line joining the centre to the point of tangency and the tangent is always 90o. Fig 1 shows all the above elements. Concentric circles: When two or more circles (drawn) having common centre, they are called concentric circles. Ball bearing is the best example of concentric circles. (Fig 2)
Engineering Drawing : (NSQF) Exercise 1.5.19 67 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.5.20 Engineering Drawing
Drawing of geometrical figures - Practice of square, rectangle, parallelogram, rhombus and circle
Follow the procedures and construct quadrilaterals on A3/ • 'A' as centre and AB as radius, draw an arc. The arc A4 sheets. cuts the circle at D. Procedure • Similarly draw an arc with centre D with radius AB and get point C. Square • Join AD, DC & CB and complete the square. 1 1st method (Fig 1): A square of side 50 mm by erecting perpendicular. 3 3rd method (Fig 3): A square of side 60 mm long by erecting perpendicular and also using 45° • Draw a line AB 50 mm long. setsquare. • 'A' as centre, draw an arc of convenient radius 'r' • Draw line AB equal to 60 mm. touching the line AB at 'P' as shown in Fig 1. • Erect perpendicular from A and B using 60° or 45° • 'P' as centre and radius 'r' draw another arc cutting the setsquare. earlier drawn arc at `Q'. • Draw 45° from A and B, cutting perpendicular lines at C • 'Q' as centre and radius 'r', draw another arc cutting at and D. 'R'. • Join A,D,C and B. ABCD is required square. • Bisect QR at S and extend. • Mark 50 mm on AS extended line. AD = 50 mm. • From points B and D, draw parallels to AD and AB and complete the square ABCD.
4 Square having diagonal 60 mm (Fig 4) • Draw horizontal and vertical centre lines intersecting at '0'. • '0' as centre, draw a circle of radius 30 mm passing through centre lines at A,B,C and D. 2 2nd method (Fig 2): A square of side 60 mm using • Join points A-B, B-C, C-D and D-A. ABCD is the 45° setsquare and compass. required square, whose diagonal is 60 mm.
• Draw a horizontal line AB = 60 mm long. • From points A and B, using 45° setsquare, draw 45° lines both intersecting at '0'. Draw a circle of radius OA or OB with centre '0'. 68 Copyright Free. Under CC BY License. 5 Rectangle (Fig 5) • D as centre, draw an arc of radius equal to AB. Side AB = 75 mm, side AD = 45 mm using setsquare and • 'B' as centre, draw an arc of radius equal at AD, upwards compass. such that they meet at a point 'C'. • Draw the side AB equal to 75 mm. • ABCD is the required parallelogram. • Erect perpendiculars at A and B. • Mark off a height 45 from A and B, at D and C. • Join C and D to complete the rectangle.
8 Parallelogram (Fig 8) Parallelogram - Side AB = 60 mm
Diagonal AC = 90 mm ABC = 120° • Draw a line AB = 60 mm. 6 Rectangle - Diagonal - 60 mm and one side 20 mm 1st method (Fig 6a) • Draw a line from B at angle of 120° to AB. • Draw a line AB 60 mm. • 'A' as centre with radius 90 mm, draw an arc cutting 120° line from B at C. • Draw a circle with AB as its diameter. • `C' as centre, radius = AB, draw an arc. • 'A' as centre, draw an arc of R20, cutting the circle at D. • Similarly `A' as centre and BC as radius, draw another • Join AD and BD. arc, both arcs meet at `D'. • Draw AC parallel to DB. • Join AD and DC. • Join BC and complete the rectangle. ABCD is the required parallelogram. 2nd method (Fig 6b) • Draw a line AD = 20 mm long. • Draw perpendiculars from A and D upwards. • A and D as centres, draw arcs of 60 mm radius cutting at B and C. • Join BC. ADBC is the required rectangle of side 20 mm and diagonal 60 mm.
9 Parallelogram (Fig 9)
7 Parallelogram (Fig 7) Sides = 75 mm and 40 mm Sides AB = 55 mm, BC = 40 mm and vertical height = 30 mm. Angle between them: 50° • Draw the line AB 55 mm long. • Draw line AB 75 mm long. • A and B as centres and radius (R) 30 mm, draw arcs • Draw line AD equal to 40 mm and 50° angle to AB. above the line. Engineering Drawing : (NSQF) Exercise 1.5.20 69 Copyright Free. Under CC BY License. • Draw a common tangential line (parallel to base AB) to the arcs. Angle CAB = • A and B as centers, draw an arc of 40 mm radius cutting the line at D and C. • Draw the diagonal AB equal to 80 mm. ABCD is the required parallelogram. • Set an angle of 25° at A and B and draw the lines, meeting at C. 10 Rhombus (Fig 10) • Join AC and BC. Diagonals AB = 80 mm • Draw AD parallel to CB. CD = 50 mm • Draw BD parallel to CA. • Draw a line AB equal to 80 mm ABCD is the required rhombus. • Draw perpendicular bisector of AB, passing through 0. Check • mark OC = OD = 25 mm. Join CD cutting AB at 0 measure • Join the points AC, CB, BD and DA to complete the rhombus. A0 = 0B; C0 = 0D Check All the four angles at 0 are right angles. AC = CB = BD = DA i.e. all the 4 sides are equal. Further practice Angle ACB = Angle ADB and 1 Construct a square of side 50 mm using compass and setsquare. Angle CAD = Angle CBD 2 Construct a square whose diagonal is 60 mm using compass and setsquare. 3 Construct a rectangle given diagonal and side are equal to 60 mm and 20 mm. 4 Construct a rhombus of side 75 mm and one angle is 50°. 5 Construct a parallelogram given sides 75 and 40 mm angle 50°. 6 Construct a parallelogram given side 60 mm, diagonal 90 mm and angle 120°. Draw the pattern drawings given in the workbook. 11 Rhombus (Fig 11) 1 Diagonal AB = 80 mm ACB = 1300 Let the diagonal is equal to 80 mm and the angle is 130°. Since sum of the angles in a triangle is 180°.
Angle ACB + Angle CBA + Angle CAB = 180°
Therefore Angle CAB = Angle CBA =
70 Engineering Drawing : (NSQF) Exercise 1.5.20 Copyright Free. Under CC BY License. 23
Circles and arcs
Follow the procedures and construct the following in the work book practice sheets of Ex.No.1 to 12. Procedure 1 Draw a tangent to a given circle of 50 mm at any point `P' on it. (Fig 1) • Draw a circle of 50 with `O' as centre. • Mark the given point `P' on the circumference of the circle. • Join OP. • Draw a line RS perpendicular to PO through `P'. 3 Draw an arc of given radius (R 20 mm) to touch the • RS is the tangent at `P'. given lines which make an acute angle between them (assume 60°). (Fig 3) • Draw an acute angle BAC (60°). • Draw a horizontal parallel line EF at a distance equal to the given radius (20 mm). • Draw another angular parallel line GH at a distance of given radius 20 mm. Both the parallel lines drawn meet at `O'. • With `O' as centre and `r' as radius (20 mm) draw an arc touching both lines AB and AC.
2 Draw an arc of given radius (R 20 mm) to touch to two straight lines (50 mm each) at right angles. (Fig2) • Draw the lines AB and AC (50 mm each) at right angles. • With `A' as centre and given radius (R 20 mm) draw an arc to cut lines AB and AC at E and F. • With E and F as centres and the radius given (R 20 mm), draw arcs to intersect each other at `O'. • Use `O' as centre and with same radius (R 20) draw a curve (arc) which will just touch the given lines AB and AC.
Engineering Drawing : (NSQF) Exercise 1.5.20 71 Copyright Free. Under CC BY License. 4 Draw a loop of 3 circles pattern. (Fig 4) • Mark centres A,B & C. • Draw any line MN and mark points A,B and C. So that • Join AB, BC & CA and form triangle ABC. AB = 20 mm and BC = 25 mm. • Bisect any two angles of the triangle. Bisectors cut the • With 'A' as centre draw concentric circles of dia 15 mm opposite sides AB and BC at F and G. and dia 20 mm. • 'A' as centre and AF as radius draw a circle. • With 'B' as centre draw concentric circles of 20 mm • 'B' as centre and BF or BG as radius draw another and 25 mm. circle. • With 'C' as centre draw concentric circles of 25 mm • 'C' as centre and CG as radius draw the third circle. and 30 mm. • Erase unwanted part of the circles to form the pattern.
5 Draw the cam as per dimensions given. (Fig 5)
• Draw a vertical line and mark the points C1C2 such that
C1C2 = 84 mm. •C as centre, draw an arc of radius 56 mm (100-44) and 1 7 Draw external tangents to circles of dia 40 and 30 C as centre, draw another arc of radius 78 mm (100- 2 and centre distance 60 mm. (Fig 7) 22). Both arcs cut at C3.
• Similarly obtain a point C4 by drawing two arcs of radii
84 mm (44 + 40) and 62 mm (22 + 40) from points C1 and
C2.
• Draw a circle of radius 44 mm with C1 as centre and draw
a circle or radius 22 mm with C2 as centre.
• Produce C1C2 and get points A and B.
•C3 as centre and radius BC3 (100 mm) draw an arc.
•C4 as centre and radius 40 mm draw an arc.
• Draw a circle of R10 with centre C2. • Rub off the unwanted lines and complete the pattern. • Draw a line and mark two points C1 and C2 at 60 mm. • Draw two circles of dia 40 and dia 30 with centre marked
as C1 and C2.
• On dia 40 circle (D1) draw a concentric circle of dia 10
(D3) (dia 40 - dia 30).
• From centre C2 draw a line 't' touching circle D3 at P.
• Join C1 and P (angle P is right angle).
• Extend line C1, P upto the circle D1 meeting at P1.
• Draw C2P2 parallel to C1P1.
• Join P1 and P2 forming the (common) tangent T1 to circle
D1 and D2.
• Similarly draw tangent T2. Tangents T1 and T2 are called 6 Draw three circles tangential to each other if external tangents. centres A,B & C are given. (Fig 6)
72 Engineering Drawing : (NSQF) Exercise 1.5.20 Copyright Free. Under CC BY License. 8 Draw internal tangents to circles of same diameter Draw the figures in A3/A4 Sheets (Fig 10 - Fig 12) 40 each and centre distance 60 mm. (Fig 8) 10
• Mark two points C1 and C2 60 mm apart.
• Draw circles of 40mm with centres C1 and C2.
• Mark 'A' the midpoint of C1C2 .
• Bisect C1A and mark it as B.
• 'B' as centre C1B as radius, draw an arc and get points
P1 and P2.
• 'A' as centre AP1 as radius, draw an arc and get points
P3 and P4.
• Join P1P4 and P2P3.
• Mark them as T1 and T2, the internal tangents.
11
9 Draw tangential curves for the circles of diameters 30 mm, 20 mm and centre distance 60mm. (Fig 9)
• Mark centres C1 and C2 at a distance of 60 mm.
• Draw the given circles of dia 30 and dia 20 on C1 and C2.
•C1 as centre and radius 35 (R15 + R20), draw arcs on either side of horizontal centre line.
•C2 as centre and radius 30 (R10 + R20), draw arcs
cutting the arcs R35 at C3 and C4.
•C3 and C4 as centers, with R20, draw arcs forming the arc tangential curves to the circles. 12
Engineering Drawing : (NSQF) Exercise 1.5.20 73 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.5.21 Engineering Drawing
Drawing of geometrical figures - Different polygons and their values of included angles. Inscribed and circumscribed polygons
Polygon is a plane figure bounded by many (usually five or more) straight lines. When all the sides and included angles are equal, it is called as a regular polygon. (Fig 1)
Names of polygons: Polygons are named in terms of their number of sides as given below: (Fig 2)
Name No. of sides Inscribed polygon Pentagon Five sides An Inscribed polygon might refer to any polygon which is inscribed in a shape. A cyclic polygon, which is inscribed Hexagon Six sides in a circle (the circumscribed circle). A midpoint polygon of Heptagon Seven sides another polygon. Octagon Eight sides Circumscribed Polygon Nonagon Nine sides A Circumscribed polygon is a polygon in which each side is a tangent to a circle. The circle is inscribed in the polygon Decagon Ten sides and the polygon is circumscribed, about the circle (It is a Undecagon Eleven sides circle in a polygon). Duodecagon Twelve sides Circumscribed literally means ‘to draw around’ a circumscribed circle of a triangle for example is the circle that passes through all three vertices, usually called the circumcircle. A Circumferential figure is a shape drawn out side another shape. For a polygon to be inscribed inside a circle all of its corner, also known as vertices, must touch the circle. If any vertex fail to touch the circle, then it is not called inscribed shape. Types of polygon PROCEDURE 1 Regular heptagon of side 25 mm. Semi-circular method - Type A (Fig 5) • Draw a line AB equal to 25 mm. Properties of polygon • Extend BA to a convenient length. • All corners of a regular polygon lie on the circle. The • `A' as centre and radius AB describe a semi-circle. sides of a regular polygon will be tangential to the circle • Divide the semi-circle into seven equal parts (number drawn in side. (Fig 3) of sides) using divider. • The sum of the interior angles of a polygon is equal to • Number the points as 1,2,3,4,5,6 starting from `P'. (2 x n - 2) x rt angle, where n is the number of sides. • Join A2 • The sum of exterior angles of a polygon is equal to 360°. • Draw the perpendicular bisectors from 2A and AB • The sum of the interior angle and the corresponding intersecting at 0. external angle is 180°. (Fig 4) • `0' as centre and OA or OB as radius describe a circle. 74 Copyright Free. Under CC BY License. • Mark point `5' at the middle of points `4' and `6'. • Set off 6-7 and 7-8 equal to 4-5. • Mark the points C,D,E,F and 2 on the circle such • Point `7' as centre and 7-A as radius draw a circle. that BC = CD = DE = EF = F2 = AB. • On the circumference set off BC, CD, DE, EF, FG • Join the line BC, CD, DE, EF and F2. and GA equal to AB. • ABCDEF2 is required heptagon. • Join BC, CD, DE, EF, FG and GA and complete the 2 Semi-circle method - Type B (Fig 6) heptagon. Follow the procedure upto dividing the semi-circle into 4 Pentagon inside a circle of diameter 60 mm. (Fig 8) number of equal parts. (Ex.1)
• Draw the line AH equals to 60 mm. (Diameter of • Join A2 circle) • Join A3, A4, A5 and A6 and extend to a convenient • `O' as centre OA as radius describe a circle. length. • Divide AH into 5 equal parts (as many equal parts as • With centre `B' and radius AB draw an arc cutting A6 the sides). extended line at `C'. • A and H as centres, AH as radius describe arcs • `C' as centre and same radius, draw an arc cutting A and H as centres, AH as radius describe arcs the line A5 at `D'. intersecting at `P'. • Locate the points E & F in the same manner. • Join P2 and extend it to meet the circle at `B'. • Join BC, CD, DE, EF and F2. • Set off BC, CD, DE, EF equals to AB on the circle. • ABCDEF2 is the required heptagon. • Join the points. 3 Perpendicular bisector method. (Fig 7) • ABCDEF is the required pentagon. • Draw a semi-circle on line AB, the side of the 5 Pentagon outside a circle of diameter 50 mm. (Fig 9) polygon. (In this case it is heptagon) • O as centre and OF as radius describe a circle of dia • Draw a perpendicular bisector of AB which cuts the 50 mm. semi-circle at point `4'. • Draw the line DF vertically beyond the top of the • Describe an arc with `B' as centre and AB as radius. circle. The arc cuts the perpendicular at `6'. Engineering Drawing : (NSQF) Exercise 1.5.21 75 Copyright Free. Under CC BY License. 8 Across flats method (Fig 12)
• Divide the circle into 10 equal parts. (Twice as many equal parts as the number of sides) • Points 1,3,5,7 and 9 are the tangent points of the pentagon. • Join 02, 04, 06, 08, 010 and extend to a convenient length. • Draw a tangent to the circle through point 1 (F). • The tangent cuts the lines 0-2 and 0-10 lines at A&B. Hexagon, distance across flat of 45 mm • In same manner draw tangents on points 3,5,7,9 & locate C,D & E. • Draw a circle of 45. (45 mm is the size across flat) • Join BC, CD, DE, EA • Draw two horizontal tangents BC and FE. • ABCDE is the required pentagon. • With 60° setsquare draw four tangents, touching the horizontal tangents. 6 Arc method • Mark the corners A,B,C,D,E and F. Hexagon of side 32 mm (Fig 10) ABCDEF is the required hexagon. 8 Octagon special method (Fig 13)
• Draw a circle of radius 32 mm. • Mark the diameter AD • With same radius, A and D as centres. draw two arcs cutting the circle at points B,F,E & C Octagon of side 36 mm. respectively. • Draw a horizontal line AB equals to 36 mm. • Join AB, BC, CD, DE, EF and FA. • Set an angle of 1350 (or 450) at A and B. ABCDE is the required hexagon. • A and B as centres, with radius AB, draw arcs, 7 Arc method (Fig 11) cutting the lines at H and C. Hexagon inside a circle of diameter 60 mm (inscribing) • Draw vertical lines from H and C upwards. • Draw a line FC equal to 60 mm (Diameter of circle). • Mark length HG and CD equal to AB. • 'O' as centre describe a circle on the diameter FC. • From point G draw a line GE parallel and equal to BC. • F as centre FO as radius draw an arc at A. • From point D draw a line DE parallel and equal to AH. • 'A' as centre, same radius draw an arc at B. • Join FE. • In the same manner set the points C,D & E. • All the sides are equal and interior angles are equal. • Join AB, BC, CD, DE, EF and FA. ABCDEFGH is octagon required. ABCDEF is the required hexagon. 76 Engineering Drawing : (NSQF) Exercise 1.5.21 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.6.22 Engineering Drawing
Lettering and numbering - Single stroke, double stroke and inclined
Apart from graphical elements (lines, arcs, circles etc) Lower case letters and numerals technical drawings will also contain written informations. Width Letters/Numerals Width These written informations are referred as “lettering”. (W) Styles of lettering: Many styles of lettering are in use to 1i1d day. However, a few styles which are commonly used are 3 j,l 3d shown in figure 1. 4 f,t,l 4d 5 c,r 5d 6 a,b,d,e,g,h,k,n,o,p,q,s,u,v;3;5 6d 7 a,0 (zero), 2,4,6,7,0,8,9 7d 9m9d 10 w 10d
The width of different letters in terms of stroke (line) is as follows: Uppercase Lettering BIS SP: 46-2003
Width (W) Capital letters 1I Standard heights/Width: The standard heights 4J recommended by BIS SP: 46-2003 are in the progressive ratio of “square root 2”. They are namely 2.5 - 3.5 - 5 - 7 - 5 C,E,F,L 10 - 14 and 20 mm. The height of lower case letter (without 6 B,D,G,H,K,N,O,P,R,S,T,U & Z tail or stem) are 2.5, 3.5, 5, 7, 10 and 14 mm. 7 A,M,Q,V,X,Y There are two standard ratios for the line thickness “d”. They are A & B. In A = line thickness (d) is h/14 and in 9W B=line thickness (d) is h/10. Lower case letters and numerals Lowercase means small letters, as opposed to capital letters. The word yes, is for example, is in lowercase, Width (W) Letters/Numerals while the word YES is in upper case. For many programmes, this distinction is very important. Programmes 1i that distinguish between uppercase and lowercase is 2l said to be case sensitive 3 j,l The width of different letters in terms of “d” is as follows: 4 c,f,r,t Lettering A 5 a,b,d,e,g,h,k,n,o,,q,s,u,v,x,y,x Width Capital letters Width (W) 0,2,3,5 to 9 1I1d 0,2,3,5 to 9 5 J,L 5d 6 a,4 6 C,E,F 6d Fig 2 & 3 shows the sequence of printing single stroke 7 B,D,G,H,K,N,O,P,R,S,T,U & Z 7d lower capitals and capital letters in vertical style. 8 A,Q,V,X,Y 8d Inclined letters (Fig 2) are drawn at an angle of 15° towards right side, the proportion being the same as of vertical 9M9dlettering. 12 W 12d Fig 2 shows double stroke letters also.
77 Copyright Free. Under CC BY License. Standard letters to suit the nature of instructions, the sizes should be selected. All the lettering should be printed, so that they are read/viewed from the bottom of the drawing. Lettering improves the appearance and legibility of the drawing. Always maintain uniform lettering (letters and numerals) which can be reproduced within reasonable time with ease. In machine drawing ornamental lettering should never be used.
Spacing of letters: Recommended spacing between character, minimum spacing of base lines and minimum spacing between words as per BIS SP: 46-2003 is given below in figure No.4 and Table 1 & 2.
TABLE 1
Lettering A (d = h/14) Values in millimetres Characteristic Ratio Dimensions
Lettering height h (14/14)h 2.5 3.5 5 7 10 14 20 Height of capitals Height of lower- c (10/14)h - 2.5 3.5 5 7 10 14 case letters (without stem or tail) Spacing between a (2/14)h 0.36 0.5 0.7 1 1.4 2 2.8 characters Minimum spacing b (20/14)h 3.5 5 7 10 14 20 28 of base lines Minimum spacing e (6/14)h 1.06 1.5 2.1 3 4.2 6 8.4 between words Thickness of d (1/14)h 0.18 0.25 0.35 0.5 0.7 1 1.4 lines
Note: The spacing between two characters may be reduced by half if this gives a better visual effect, as for example LA, TV; it then equals the line thickness d.
78 Engineering Drawing : (NSQF) Exercise 1.6.22 Copyright Free. Under CC BY License. TABLE 2
Lettering B (d = h/10) Values in millimetres Characteristic Ratio Dimensions
Lettering height h (10/10)h 2.5 3.5 5 7 10 14 20 Height of capitals Height of lower- c (7/10)h - 2.5 3.5 5 7 10 14 case letters (Without stem or tail) Spacing between a (2/10)h 0.5 0.7 1 1.4 2 2.8 4 characters Minimum spacing b (14/10)h 3.5 5 7 10 14 20 28 of base lines Minimum spacing e (6/10)h 1.5 2.1 3 4.2 6 8.4 12 between words Thickness of d (1/10)h 0.25 0.35 0.5 0.7 1 1.4 2 lines
Note: The spacing between two characters may be reduced by half if this gives a better visual effect, as for example LA, TV: it then equals the line thickness d.
Lettering
Note: Print letters/numerals in workbook (Ex.1 • Draw horizontal parallel lines (thin lines) of 10 mm to 6) as instructed below: distance. 10 mm distances denotes the height of the Procedure letter. 1 Print 10 mm single stroke capital letters and numerals • Mark the width of the letters recommended by BIS in vertical style using either scale or setsquare and by (IS:9609-1983) free hand. The width of different letters in terms of `d' is as follows: `d' indicates stroke thickness i.e d: h/ 10.
Width Capital letters (W)
1I 4J 5 C,E,F,L 6 B,D,G,H,K,N,O,P,R,S,T,U & Z
7 A,M,Q,V,X,Y 9W
Engineering Drawing : (NSQF) Exercise 1.6.22 79 Copyright Free. Under CC BY License. For curved letters use smooth free hand curve. Refer lettering practice theory and complete the printing of letters and numerals. Print straight line letters using either scale or setsquares. 5 Print the following statements in 5 mm size. To maintain the uniform thickness of line, use 1 All dimensions are in mm conical point soft grade pencil and avoid too 2 Ask if in doubt much of sharpness. 3 Six holes diameter 8 mm equally spaced 60 mm Guidelines of both top and bottom should al- pitch circle diameter. ways be drawn with sharp pencil. 4 This drawing confirms to IS:9609-1983
Numerals 2.1 (Fig 2) 5 Bureau of Indian Standards (BIS) is our national standard. 6 General deviations as per IS:2012 (medium) 7 All thick lines - 0.5 mm 8 Chamfer to bottom of thread. 9 Rough mill the surface marked `X'. 10 Punch roll number and part number. • Follow the same procedure of letters. • Calculate the width of the each letters. • `h' is height of numerals and `d' is the stroke thickness. • Draw the guidelines for the required size. • Width of numerals in terms of `d' is as follows shown in • Mark the width and spacing for each letter. square grid (Fig 3). • Draw vertical guidelines. • Print the letter free hand, using HB pencil.
Print letters and numerals (1 to 5) according to the procedure given in theory book. Practice 1 to 5 1 Print letters A to Z and numerals 1 to 0 in vertical style. 2 Print 10 mm single stroke capital letters and numerals 10 mm capital letters, 10 mm numerals. in inclined style (Fig 4). 2 Print letters A to Z and numerals 1 to 0 in inclined style. 10 mm capital letters, 10 mm numerals. 3 Print letters and numerals vertical and inclined style. 5 mm capital letters. 4 Print lower case letters 5 mm size in vertical and inclined style. 5 Print the following statements in 5 mm size letters and numerals. • All dimensions are in mm. • Six holes diameter 8 mm equally spaced 60 mm pitch circle diameter.
• Follow the same procedure of vertical capital letters and • This drawing confirms to BIS SP: 46-2003. numerals. • Bureau of Indian Standards (BIS) is our national • Mark inclined lines at an angle of 15° towards right or standard. 75° from horizontal. • All thick lines - 0.5 mm. 3 Print letters and numerals, vertical and inclined style. • Chamfer at bottom of thread. Size 5 mm - Capital letters. • Rough mill the surface marked `X'. 4 Print 5 mm lower case letters and numerals both in • Punch roll number and part number. vertical and inclined style.
80 Engineering Drawing : (NSQF) Exercise 1.6.22 Copyright Free. Under CC BY License. Practice the following lettering exercises in A3/A4 paper as per the given ratio
1 Single stroke inclined letters of ratio 7:6, 7:5, 7:4, 7:3, 7:1 (Fig 1)
Engineering Drawing : (NSQF) Exercise 1.6.22 81 Copyright Free. Under CC BY License. 2 Single stroke vertical letters of ratio 7:6, 7:5, 7.4, 7:3, 7:1 (Fig 2)
82 Engineering Drawing : (NSQF) Exercise 1.6.22 Copyright Free. Under CC BY License. 3 Double stroke vertical letters of ratio 7:6, 7:5, 7.4, 7:3, 7:1 (Fig 3)
Engineering Drawing : (NSQF) Exercise 1.6.22 83 Copyright Free. Under CC BY License. 4 Double stroke inclined letters of ratio 7:6, 7:5, 7.4, 7:3, 7:1 (Fig 4)
84 Engineering Drawing : (NSQF) Exercise 1.6.22 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.7.23 Engineering Drawing
Dimensioning - Definition, and its types, types of arrow heads and leader line with text
Importance of dimensioning: Any Component or product Size dimensions: Give the size of a component, part, manufactured should be confirm to its specification. In hole, slot, depth, width, radius etc. fact, without specification of product, there cannot be eg: L1, L3, H, h1, S etc. (Fig 2) production. In engineering industry, all manufacturing is controlled by the technical specification of product or Location dimension: Give or fixes the relationship of the components. features. viz centre of holes, slots and any significant Technical specification provides complete information on forms. (Fig 2) the shape, size, tolerance, finish, material and other eg: L4, L5, L6 technical aspects such as heat treatment, surface coating and other relevant information required to manufacture a component. In most cases technical specifications of components are given in the form of a technical drawing while shape is described by various types of views i.e Orthographic, pictorial and perspective projection and size is given by dimensions. Definitions related to dimensioning Dimension: It is a numerical value expressed appropriate unit of measurement and indicated graphically on technical drawings with lines, symbols and notes. Dimensions are classified according to the following types: Feature: It is an individual characteristic such as flat Functional dimension (F): It is a dimension which is surface. Cylindrical surface, shoulder, screw thread, a slot, essential to the function of the component or space. They a curve or profile etc. (Fig 3 & 4) are generally shown with limits. (Fig 1)
End product: It is a part ready for direct use or assembly or it can be a part ready for further process. e.g a casting, shoulder screw etc. (Fig 4)
Non-functional dimension (NF): It is a dimension which The unit of measurement in general, unless or is not essential for the function of the component or space. otherwise specified is mm (millimetres). On Auxiliary or Reference dimension (AUX/REF): It is the the dimensions of drawings the abbreviation dimension given for information only. It is derived from the mm is omitted and a general note is given in an values given on the drawing or related documents and it appropriate corner as "All dimensions are in does not given in the production or inspection. (Fig 1) mm". 85 Copyright Free. Under CC BY License. Elements of dimensioning • Extension line - a • Dimension line - b • Leader line - c • Termination of dimension line - d • The original (starting point) indication and the dimension (a). Extension line: It is a thin line projecting from the feature and extending beyond the dimension line. (Fig 5)
It is normally perpendicular to the feature being dimensioned, but may be drawn obliquely as shown for dimensioning tapers, parallel to each other. (Fig 6)
When construction line are required to be shown for practical purposes of the intersecting projection lines Leader line: It is a thin continuous line. It connects a note extend beyond their point of intersection. (Fig 7) or dimension with the features to which it applies. (Fig 10) Termination and Origin indication: The size of the terminations (arrow heads/oblique strokes) shall be proportional to the size of the drawing. Only one style of arrow head shall be used on a single drawing. However, where the space is too small for the arrow heads, it may be substituted by a dot or by an oblique line. Arrow heads are Extension lines (Projection lines) should not cross the drawn as short lines forming barbs at any convenient dimension lines, but where not possible the lines should included angle between 15° and 90°. They may be open, not break. (Fig 8) closed or closed and filled in. Oblique strokes drawn as short line inclined at 45°. (Fig 9) Dimension line: These are thin continuous lines, terminated at ends by arrow heads, dots or oblique lines touching the Indicating dimensional values on drawings: All extension line. (Fig 9) dimensional values shall be shown on drawings in characters of sufficient size to ensure complete legibility on the Dimension line may cut or cross another dimension line original drawings as well as on reproductions made from where there is no other way. micro-filming. Dimension to the hidden lines be avoided. (Fig 10) They shall be placed in such a way that they are not Arrow heads may be placed outside where space is crossed or separated by any other line on the drawing. insufficient. 86 Engineering Drawing : (NSQF) Exercise 1.7.23 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.7.24 Engineering Drawing
Dimensioning and its practice - Methods of dimensions and position of dimensioning (aligned, unidirectional)
Methods of indicating values: There are two methods • Dimensioning by co-ordinates used for indicating the values. Only one method should be used on any one drawing. • Combined dimensioning. Method 1 Dimensional values shall be placed parallel to their dimension lines and preferably near the middle, above and clear of the dimension line. However, values shall be indicated so that they can be read from bottom or from the right-hand side of the drawing. Dimension lines are not broken. Dimensioning of angles also given in the same way. (Fig 1 & 2) This method is known as aligned system of dimensioning.
Chain dimensioning: It is used where the possible accumulation of tolerances does not infringe (effect) on the functional requirement of the component. (Fig 5)
Method 2 Unidirectional system Dimensional values shall be indicated so that they can be read from the bottom of the drawing sheet. Non-horizontal dimension lines are interrupted, preferably near the middle Dimensioning from a common feature is used where a so that the value can be inserted. (Fig 3&4). This method number of dimensions of the same direction relate to a is termed as unidirectional system of dimensioning. common origin. Arrangement and indication of dimensions Dimensioning from a common feature may be executed as parallel dimensioning or as superimposed running The arrangement of dimensioning on a drawing shall dimensioning. indicate clearly the design purpose. Parallel dimensioning: Dimensions of features are taken The arrangements of dimensioning are: from one datum/common origin and are shown parallel to • Chain dimensioning other and placed, so that the dimensional values can easily • Dimensioning from a common feature be added in Fig 6. 87 Copyright Free. Under CC BY License. Methods of dimensioning common features Dimensioning Tapered parts: When dimensioning Superimposed running dimensioning (Progressive tapered part, extension lines be at an angle and parallel to dimensioning): It is a simplified dimensioning also each other. Dimension line be drawn parallel to the feature Cumulative error is controlled. It starts from one origin with to be dimensioned. (Figs 10 & 11) They may sometimes arrow heads in one direction only. This may be used where be shown with large dia and or MT number. there are space limitations and where no legibility problems would occur. The origin indication is placed appropriately and the opposite ends of each dimension line shall be terminated only with an arrow head. It may be advantageous to use superimposed running dimensions in two directions. (Fig7)
Dimensioning by co-ordinates: This system is much used for components, produced on jig boring machine. Two edges are taken as datum. (references) Instead of dimensioning in superimposed way, same may be tabulated and given. (Fig 8) Dimensioning smaller width: Arrow heads are replaced by oblique lines. (Fig 12)
This method is useful in indicating places/positions in To avoid placing dimensions too far away from feature, country, city and site plans. dimension lines are drawn closer and not fully. (Fig 13) Combined dimensioning: Dimensions are given in chain Dimensioning cylindrical and spherical features: dimensioning and parallel dimensioning. Common feature Cylindrical features have diameter and length whereas is combined. (Fig 9) sphere has a diameter only. 88 Engineering Drawing : (NSQF) Exercise 1.7.24 Copyright Free. Under CC BY License. Dimensioning equidistant features: Where equidistant features or uniformly arranged elements are parts of the drawing, specification of the dimensioning may be simplified. Linear spacings may be dimensioned as in Fig17a&b.
Diameter may be indicated by any one of the abbreviation D, Dia, d, dia or and radius may be indicated by R, r, Rad or rad by square. Any one abbreviation or symbol on a drawing may be indicated by SQ or . The length if any required to give along with dia, if it is shown as ...x... long. (Fig 14)
- Diameter R - Radius - Square SR - Spherical radius S - Spherical diameter
Dimensioning angles and Angular spacings Equal angles eg. 4 x 10° = 40° Equal centre distances eg. 4 x 10 = 40. (Fig 18)
Dimensioning a chord: For dimensioning of chord, refer Fig 15. It is shown as linear size.
When the drawing is clear, symbols or abbreviation viz. dia, Pcd and angle can be omitted. (Fig 19) Dimensioning an arc/radius: A small arc is shown over the dimension value, while dimensioning an arc. (Fig 16)
Engineering Drawing : (NSQF) Exercise 1.7.24 89 Copyright Free. Under CC BY License. Dimensioning periphery: The features on the periphery can be shown as given in the figure, indicating width, depth and number of slots. (Fig 20)
Dimensioning repeated features: When elements of same size occur, but not of same pitch be shown as in Fig21.
Countersinks and counterbore (IS:10968-1984): For simplification, the holes are indicated by centre lines and marked by different letters to different type/size of hole. The holes maybe plain, through blind, tapped, countersink of counterbore. (Fig 22) Dimensioning chamfers and undercuts: Chamfer of 45° may be shown by leader line indicating chamfer width and angle or by dimension line with chamfer width and angle. (Figs 23 & 24) Dimensioning undercut: Dimensioning undercuts are dimensioned either by normal dimensioning the width i.e u/ c 4 x 2 or by leader terminating horizontally u/c 4 x 2. (Fig23) 90 Engineering Drawing : (NSQF) Exercise 1.7.24 Copyright Free. Under CC BY License. Other indications: In order to avoid repeating the same dimensional values or to avoid long leader lines, reference letters/numbers may be used in connection with an explanatory table or note. In such cases leader lines may be omitted. (Fig 25)
In partially drawn views and partial sections of symmetrical parts the dimension lines that need not cross the axis of the symmetry are shown extended slightly beyond the axis of symmetry. The second termination is then omitted. (Fig26)
Principles and application of dimensioning: Before Where several parts are drawn and dimensioned in an proceeding to give dimensions, consider the following assembly, the groups of dimensioned in an assembly, the steps: groups of dimensions related to each parts should be kept as separate as possible. (Fig 27) • Mentally visualize the object and divide it into geometrical shapes such as prisms, cones, cylinders, pyramids etc. • Place the size dimension on each form. • Consider the relationship of mating parts and the process of production, then select the locating (reference or datum) centre lines and surfaces. • ensure that each geometrical form is located from a centre line and/or a finished surface. • Place the overall dimensions. • Add the necessary notes like surface finish, specific Dimensioning arcs by radius: Only one arrow head operations, material, fit, type of thread etc. (Fig 30) termination, with its point on the arc end of the dimension line shall be used where a radius is dimensioned. The • All dimensional information necessary to define a part arrow head may be either inside or outside of the feature or component clearly and completely shall be shown outline. (Fig 28) directly on a drawing unless this information is specified in relevant documents. Values for dimensions out of scale: After finalising sizes may require modification. Instead of re-drawing the entire • Each feature shall be dimensioned once only on a component, the dimension which is changed is marked drawing. and a thick line drawn below such size indicating this • Dimension shall be placed on the view or section that (feature) size is not to scale (NTS). (Fig 29) most clearly shows the features.
Engineering Drawing : (NSQF) Exercise 1.7.24 91 Copyright Free. Under CC BY License. The non-functional dimensions should be placed in a way which is most convenient for production and inspection. Projection lines should be drawn perpendicular to the feature being dimensioned. Where necessary, however, they may be drawn obliquely, but parallel to each other. (Fig 33)
Each drawing shall use the same unit (for example, millimetres) for all dimensions but without showing the unit symbol. In order to avoid misinterpretation, the pre-dominant unit symbol on a drawing may be specified in a note. Where other units have to be shown as part of the drawing specification ( for example, N, m for torque or kPa for pressure), the appropriate unit symbol shall be shown with Dimension line shall be shown unbroken where feature to the value. which it refers is shown broken, except in Method 2 No more dimensions than are necessary to define a part or (Unidirectional). (Fig 34) an end product shall be shown on a drawing. No feature of a part or an end product shall be defined by more than one dimension in any one direction. Exception may, however be made • where it is necessary to give additional dimensions at intermediate stages of production (for example, the size of a feature prior to carburizing and finishing). • where the addition of an auxiliary dimension would be advantageous. Production processes or inspection methods should not Avoid intersection of projection lines and dimension lines, be specified unless they are essential to ensure satisfactory where unavoidable neither line shall be shown with a break. functioning or interchangeability. (Fig 35) Functional dimensions should be shown directly on the A centre line or the outline of a part shall not be used as a drawing wherever possible. (Fig 31) dimension line but may be used in place of a projection line. Occasionally indirect functional dimensioning is justified or Any one style of arrow head termination shall be used on necessary. In such cases, care shall be exercised so that a single drawing. However, where space is too small for the effect of directly shown functional dimensioning is arrow head, oblique stroke or dot may be substituted. maintained. (Fig 32) shows the effect of acceptable (Fig36) indirect functional dimensioning that maintains the dimensional requirements established by (Fig 31) . 92 Engineering Drawing : (NSQF) Exercise 1.7.24 Copyright Free. Under CC BY License. Values for dimensions out of scale, except where break lines are used shall be underlined with a straight thick line. Use chain dimensioning where the possible accumulation of tolerances does not infringe effect on the functional requirements of the part. Single dimension, chain dimensioning and dimension line from a common feature may be combined on a drawing if necessary. Where the size of the radius can be derived from other dimensions, it shall be indicated with a radius arrow and the symbol `R' without an indication of the value. (Fig 39)
It may be advantageous to use superimposed running dimensioning in two directions. In such a case, the origins may be as shown in Fig 40. Arrow head terminations shall be shown within the limits of the dimension line where space is available. Where space is limited, the arrow head termination may be shown outside the intended limits of the dimension line that is extended for that purpose. (Fig 37)
Only one arrow head termination, with its point on the arc end of the dimension line, shall be used where a radius is dimensioned. The arrow head termination may be either on the inside or on the outside of the feature outline for its projection line depending upon the size of the feature. (Fig38)
If it is possible to define a quantity of elements of the same size so as to avoid repeating the same dimensional value, they may be given as shown in Figs 41 & 42.
Dimensional value should be legible. Dimension of spherical features should be preceded by S or SR.
Engineering Drawing : (NSQF) Exercise 1.7.24 93 Copyright Free. Under CC BY License. If the special requirement is applied to an element or Where necessary, in order to avoid repeating the same revolution, the indication shall be shown on one side only. dimensional value or to avoid long leader lines, reference (Fig 45) letters may be used in connection with an explanatory table or note. Leader lines may be omitted. (Fig 43)
Where the location and extent of the special requirement requires identification, the appropriate dimensioning is necessary. However, where the drawing clearly shows the extent of the indication, dimensioning is not necessary. (Fig 46)
In partially drawn views and partial sections of symmetrical parts, the dimension lines that need to cross the axis of symmetry are shown extended slightly beyond the axis of symmetry. The second termination is then omitted. (Fig44)
Practice of dimensioning
1 Draw the two sheet metal templates to full scale with • Draw a rectangular block of length 80 mm and width appropriate lines use 0.5 range line thickness. (Fig 1) 50 mm in thin lines. • Incorporate the features of the template as per the given dimension. • Draw by thick lines all visible out lines. • Give dimensions and maintain the line thickness as per the line range (0.5). • Complete the figure and remove the unwanted lines. 2 Draw the figures given. Maintain the types of lines as per the B.I.S and choose correct line thickness. (Fig2) • According to the given dimensions, draw the figures given in Fig 2. • Select the appropriate lines and maintain uniformity. • Remove (erase) unwanted lines, arcs and complete the drawing.
94 Engineering Drawing : (NSQF) Exercise 1.7.24 Copyright Free. Under CC BY License. 4 To the given drawing of the profiled sheet metal as shown in Fig 4a, give the dimensions in the unidirectional system. • Place the horizontal dimensions above and middle of the dimension line without break. • Break the dimension in the middle of all non- horizontal dimension lines. (Fig 4b)
3 To the given drawing of the profile sheet metal as shown in Fig 3, place the dimensions in the aligned system. (Fig3a) • Draw the drawing of the sheet metal to 1:1 scale. 5 Motor cycle engine gasket is shown in figure 5. There • Draw the extension lines in continuation of outlines. are some mistakes in dimensioning. Reproduce the • Draw the dimension lines. (Fig 3b) same in A3/A4 sheet provided and correct the mistakes according to the aligned system of dimensioning. (Fig5) 6 Draw the given cover plate and give the dimensions in the aligned system. (Fig 6)
7 Draw the cover plate given in figure and place the dimensions in the unidirectional system. (Fig 7)
• Place the dimension value near the middle and above the dimension line to be read from "bottom and right hand side" of the drawing.
Note: Draw the dimension line terminations as per IS:11669-1986. 8 Draw the profiled plate given in figure having angular edge and give dimensions in aligned system. The left • Draw the arrow heads with short lines forming borbs and bottom edge represent the dimension reference at any convenient angle between 15° to 90°. line. (Fig 8) Engineering Drawing : (NSQF) Exercise 1.7.24 95 Copyright Free. Under CC BY License. 9 Draw the profiled plate sheet metal with angular edges and dimension in unidirectional system (Fig 9).
10 Draw the given distance plate and dimension in aligned system. The basic dimension of the plate is 60 mm x 80 mm (Fig 10). 11 Draw the board of 3-phase motor given and dimension in aligned system (Fig 11). 12 Draw the special cam shown in figure and dimension according to aligned system (Fig 12).
96 Engineering Drawing : (NSQF) Exercise 1.7.24 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.7.25 Engineering Drawing
Symbols preceding the value of dimension and dimensional tolerance
Combination of hole and shaft for a particular fit Introduction The limit system may be, according to the ‘Basic hole’ or ‘Basic shaft’ system. All the internal features are to be referred to as hole and the external features as shaft. Basic hole system (Fig 1) The basic hole system is the one in which the different clearances or interferences are obtained in association with various shafts with a single hole, whose lower deviation is zero i.e. the basic size of the hole is taken as standard and the diameter of the shaft is varied to get the desired fit.
Example (Fig 3): In the basic shaft system all the holes are within the tolerance zone H7. The shafts receive the tolerance necessary for achieving the desired fit on the diameter to fix couplings, bearings, worm-gear etc.
Basic shaft system (Fig 2) The basic shaft system is one in which the different clearances and interferences are obtained in association of various holes with a single shaft whose upper deviation is zero i.e. the basic size of the shaft is the maximum size of the shaft. In the basic shaft system, the shaft is taken as standard and the diameter of the hole is varied to get the desired fit.
Fit Shaft Hole Clearance h A up to H Transition h J up to N Interference h P up to Zc There are many cases in which the basic shaft system is Basic hole or basic shaft systems : Both the systems are more advantageous. This can be efficiently applied for long equally valid. In general, most of the manufacturers of shafts machined to the same size over their full length. machine tools prefer the basic hole system because it is (Smooth drawn shaft, shafts ground in centreless grinding more economical. The reason is that holes are usually machines etc.) If the shaft is to mate with atleast two parts produced in batches in mass production by fixed diameter having holes that require different types of fit, the basic tools like twist drill, reamers, taps, broaches etc. Due to shaft system is preferred. this, the machines need not be set up to obtain the proper size of the hole; setting up operations of jobs with respect to cutting tool consequently can be made quicker and cheaper. 97 Copyright Free. Under CC BY License. Example (Fig 4): A finished shaft with h6 tolerance is used Guide lines for the selection of fits are given in table - 1 and the holes of crank, bearing, gear, coupling are so tolerance that the desired fit is achieved. TABLE 1 Number of combinations for different fits In the BASIC HOLE system, the basic part is the hole, while the shaft is the mating part. Holes Fits Shaft Classification In the BASIC SHAFT system, the basic part is H6 H7 H8 the shaft, while the hole is the mating part. Clea- c - - c9 Slack running fit. ran- d - d8 d8/d10 Loose running fit. ce e e7 e8 e8/e9 Easy running fit. f f6 f7 f8 Running (normal) fit. g g5 g6 - Close running fit. h h5 h6 h7/h8 Slide Tran- j j5 j6 j7 Push. sition k k5 k6 k7 Easy keying. m m5 m6 - Tight keying. n - n6 - Light drive. Inter- p - p6 - Light press. fere- r - r6 - Medium press. nce s - s6 - Heavy drive. t - - t7 Free fit. u - - u7 Heavy press fit or shrink.
Table II to provides tolerance for various fits
TABLE II Suggested combinations of tolerance for application of various fits
Suggested Combination Hole Shaft
Slack running fits where ease of assembly is important. H8 c9 Loose running fits e.g. plummer block bearings and loose pulleys. H8 d8 General loose clearance fits (high speed) e.g. heavily loaded bearings and large electric motor bearings. H8 e8 Normal running fit e.g. gear box shaft bearings and the bearings of small electric motors. H7 f7 Precision sliding fit (not running with) e.g. piston and slide valves location fits. H7 g6 Closest clearance fit for spigots, and links, pins in mechanisms etc. H7 h6 Transition fit coupling spigots and gear rings clamped to steel hubs. H8 g7 Slight interference fit e.g. gudgeon pin in piston. H7 k6 Tight transition fit for accurate location. H7 m6 Interference fit - commutator on shaft. H7 p6 Medium driving fit - bushes etc H7 r6 Heavy driving fit e.g. permanent assemblies. H7 s6 Force fit for permanent assemblies, coupling on shaft. H7 t6 Shrink fits - e.g. loco wheels on axle. H7 u6
98 Engineering Drawing : (NSQF) Exercise 1.7.25 Copyright Free. Under CC BY License. +1500 +280 +420 +820 +570 +710 +1110 +240 +340 +660 +530 +630 +950 +230 +310 +580 +480 +560 +830 +200 +260 +460 +450 +510 +710 +180 +240 +410 +390 +440 +600 +150 +200 +360 +330 +380 +530 +130 +180 +320 +280 +330 +470 +480 +840 +1650 +720 +960 +1500 +840 +1160 +1900 +330 +540 +1050 +400 +680 +1350 +620 +800 +1240 0 +290 +340 +480 +120 +400 +460 +630 +14 +20+60 +140+270 5 +61 +98 +170 +240 +370 56 +110 +190 +650 +860 +1370 F8 E9 D10 C11 B11A11 8 +69 +125 +210 +760 +1040 +1710 7 +16 +32 +50 +95 +150 +290 +20 +68 +135 +230 +880 +1240 +2050 +75 +151 +265 +440 +360 +600 +1200 250 +54 +106 +185 +305 +460 +530 +770 0 +2 +6 5 +290 +61 +122 +215 +355 +550 +670 +1030 0 0 +10 +30 +60 +100 +340 +390 +550 0 0 0 +7 +20 +40 +65 +110 +160 +300 31.5 +63 +97 +155 +400 +83 +165 +290 +480 +440 +760 7 +12.5 +25 +39 +62 +160 +34 +64 +112 +180 +120 +170 +310 +6 +9 +18 +27 +43 +110 +24 +43 +75 +120 +205 +260 +400 7 +6 +10.5 +21 +33 +52 +130 +28 +53 +92 +149 +240 +290 +430 -40 +5 +10 +14 +25 +60 +12 +20 +39 +60 +120 +200 +330 4 -10 +10 +17.5 +35 +54 +87 +220 +47 +90 +159 +260 +170 +220 +380 1 -9 +9 +15 +30 +46 +74 +190 +40 +76 +134 +220 +140 +190 +340 16 -14 -10 -50 0 0 23 -20 -16 -9 -6 0 0 0 0 +4 +10 +20 +30 +70 +140 +270 126 -36 -14 +16 +26 +52 +81 +130 +320 +69 +137 +240 +400 +300 +480 +920 -28 -24 -19 -10 -7.5 0 0 0 0 +5 +13 +25 +40 +80 +150 +280 -144 -41 -16 +17 +28.5 +57 +89 +140 +360 72 -166 -45 -17 +18 -140 -270 -15 -11 -8 -4 +3 +6 +12 +18 +30 +75 +16 +28 +50 +78 +145 +215 +345 -480 -920 -138 -74 -300 -570 -710 -1110 -169 -113 -280 -420 -820 -123 -67 -530 -630 -950 -151 -106 -240 -340 -660 -105 -60 -480 -560 -830 -133 -93 -230 -310 -580 -93 -53 -450 -510 -710 -117 -88 -200 -260 -460 -77 -48 -400 -460 -630 -101 -76 -170 -220 -380 -58 -38 -340 -390 -550 -78 -62 -140 -190 -340 -42 -30 -290 -340 -480 -120 -170 -310 -880 -1240 -2050 -292 -172 -360 -600 -1200 -169 -87 -440 -760 -1500 -209 -103 -650 -860 -1370 -202 -130 -760 -1040 -1710 -244 -150 TABLE FOR TOLERANCE ZONES & LIMITS (DIMENSIONS IN m m) m IN (DIMENSIONS LIMITS & ZONES TOLERANCE FOR TABLE -220 -34 -71 -126 -207 -180 -240 -410 -66 -41 -59 -45 -25 -17.5 0 0 0 0 +12 +36 +72 -160 -25 -50 -89 -142 -130 -180 -320 -59 -50 -42 -33 -18 -12.5 0 0 0 0 +9 +25 +50 +8 -110 -17 -34 -59 -93 -205 -260 -400 -39 -34 -29 -23 -12 -9 0 0 0 0 + -155 -400 -60 -131 -232 -385 -480 -840 -1650 -229 -109 -108 -80 -45 -31.5 0 0 0 0 -140 -360 -54 -119 -214 -350 -400 -680 -1350 -187 -93 -98 -73 -40 -28.5 0 0 0 0 +1 -130 -320 -49 -108 -191 -320 -330 -540 -1050 -150 -78 -88 -66 -36 -26 0 0 0 0 +17 + +14.5 0 0 0 0 -15 -50 -100 -170 -260 -380 -740 -113 -63 -33 -14 +13 +23 +46 +72 +11 +12.5 0 0 0 0 -14 -43 -85 -145 -210 -280 -520 -85 -50 -28 -12 +12 +20 +40 +63 +100 + -9.5 -19 -30 -74 -190 -29 -60 -106 -174 -150 -200 -360 -48 -32 -51 -39 -21 -15 0 0 +4.5 0 0-5.5 0 -11 0 -18 -43 -5-6.5 -13 -13 -25 -21 -40 -52 -80 -130 -20 -150 -280 -41 -17 -73 -13 -117 -9 -240 -290 -4 -430 -48 +5 -41 +7.5 -35 +15 -28 +22 -15 +36 -10.5 +90 0 +20 +3 +21 +9.5 0 0 0 0 -10 -30 -60 -100 -330 -380 -530 -72 -60 -2 s6 r6 p6 n6 k6 js6 h6 h7 h9 h11 g6 f7 e8 d9 c11 b11 a11 S7 R7 P7 N7 K7 JS7 H7 H8 H9 H11 G7 Over 250 +190 +126 up toup 250 +140 +84 Overtoup Over 200 225 +159 225 +130 +109 +80 +79 +169 +50 +60 +113 +31 +33 +4 -14.5 -29 -46 -115 -290 -44 -96 -172 -285 -550 -67 0 -1030 -159 -109 -79 -60 -33 -23 0 0 0 0 +15 +50 +100 +170 +260 +380 +740 up toup 200 +122 +77 Over 180 +151 +106 up toup 180 +108 +68 Overtoup Over 140 160 +125 160 +100 +90 +65 +68 +133 +43 +93 +52 +27 +28 +3 -12.5 -25 -40 -100 -250 -39 -83 -148 -245 -460 -53 0 -770 -125 -90 -68 -52 -28 -20 0 0 0 0 +14 +43 +85 +145 +210 +280 +520 up toup 140 +92 +63 Over 120 +117 +88 up toup Overtoup 100 100 +71 120 +51 +101 +79 +59 +76 +54 +45 +37 +25 +23 +11 +3 0 -11 0 -22 -35 0 -87 0 -12 -36 -72 -120 -390 -440 -600 -93 -73 -2 Over 80 +93 +73 Over 65 +78 +62 +32 +20 +2 up toup toup 65 +53 80 +41 +59 +51 +43 +39 Over 50 +72 +60 Fromtoup 1 3 +20 +14 +16 +10 +12 +6 +10 +6 +4 +30 0 -3 -60 0 -10toup -25 0Over -60toup -2 40 -8-6 40 +59 -16 50 -14 +50 -28 +43 +42 -20 +34 -45 +3360 - +26 -120 +18 -140 -200 +17 -270 +8 -330 +2 -14 -24 0 -8 -10 -20 0-6 -16 - -25 0 -62 0 -9 -25 -50 -80 -280 -330 -470 -34 -25 -17 -8 + Overtoup Overtoup 3 6Over +27toup 6 +19 10 +23Over +15 +32 10 +20toup +23 +12 14 +28 +16 +19Over +8 14 +24 +9toup +39 +15 18 +1 +19 +34 +10 +4Over +28-4 18 to +10 up +29 +1 24 +230 +23 -8Over -4.5 +18 24 +48 +12 0 30 -9 -12 +12 +41 +5.5 +35 0 +1 -30 30 -15 0 +35 +28 -75 0 -36 +28 +22 0 -12 +15 -90 -4 +15 +6.5 -22 0 -14 -10 +2 0 -28 -28 -20 0 -60 0 -47 -30 -6 -145 -76-70 0 -215 -170 -16 -345 -240 0 -32 -27 -370 -50 - -7 -32 -95 -20 -150 -40 -290 -65 -21 -110 -16 -160 -11 -300 -5 -27 -20 -14 - up toup 355 +190toup +108 +98Overtoup 450 +73 +40 450 +232 500 +126 +18 +292 +108 0 +252 +172 +80 +132 +68 0 +45 +40 +20 0 +5 0 0 -20 0 -40 -18 0 -63 -62 0 -125 -210 -20 -720 -68 -960 -1560 -135 -226 -230 -840 -1160 -1900 -2 OverOver 315 +226Over 355 +144 +244 400 +150 +62 +272 +37 +166 +4 -18 -36 -57 up toup Overtoup 280 280 +158 315 +94 +202 +88 +170 +130toup +98 +66 +56 +36 +34 40099 +4 +16 0 +208 -16 +114 0 -32 -52 0 0 -17 -56 -110 -190 -620 -800 -1240 -190 - Nominal size range Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.8.26 Engineering Drawing
Sizes and layout of drawing sheets - Selection of sizes, title Block, its position & content and item reference on drawing sheet (item list)
Designation of sheets: The drawing sheets are designated Layout of drawing sheet: by symbols such as A0,A1,A2,,A3,A4 and A5. A0 being the As a standard practice sufficient margins are to be provided largest. Table 1 below gives the length and breadth of the on all sides of the drawing sheet. The drawing sheet should above sizes of sheets. (Trimmed and untrimmed) have drawing space and title page. A typical layout of a The relationship between two sides are same as that of a drawing sheet is shown in the (Fig 1 & 2). side of a square and its diagonal. 1 TABLE 1 Designation Trimmed size Untrimmed size A0 841 x 1189 880 x 1230 A1 594 x 841 625 x 880 A2 420 x 594 450 x 625 A3 297 x 420 330 x 450 A4 210 x 297 240 x 330 A5 148 x 210 165 x 240 EDN182611
Title Block - 1
2
EDN182612
100 Copyright Free. Under CC BY License. Title Block - 2
Title Block - 3
Engineering Drawing : (NSQF) Exercise 1.8.26 101 Copyright Free. Under CC BY License. Title Block - Position and content - 1
102 Engineering Drawing : (NSQF) Exercise 1.8.26 Copyright Free. Under CC BY License. Title Block - Position and content - 2
Item Reference on Drawing Sheet
05 TIGHTENING PIN 01 MILD STEEL
04 WORK PIECE 01 ANY MATL.
03 SCREW ROD 01 STD.
02 “U” CLAMP 01 CAST IRON
01 “V” BLOCK 01 CAST IRON
DESCRIPTION OF ITEM QTY/ASSY MATERIAL REMARKS
BILL OF MATERIALS
The drawing sheet on which the drawings to be prepared 3 Follow the same procedure for A3 drawing sheet where should be prepared first by following the procedure given the title block is to be drawn right side bottom corner below and the border dimensions remain same. 1 Take A4/A3 drawing sheet. 4 Title block to be drawn whenever the title of the drawing changes. Eg. for the geometrical construction chapter 2 Mark the borders and draw the title block as mentioned the title block may be drawn in the first sheet only where below. as on the remaining sheets borders to be drawn before they are used for preparing drawings.
Engineering Drawing : (NSQF) Exercise 1.8.26 103 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.9.27 Engineering Drawing
Method of presentation of engineering drawing - Pictorial view and isometric view Pictorial drawing: Even a common man can understand easily the shape of an object quickly by a picture or by a pictorial drawing. It is also called as three dimensional drawing. Pictorial drawings are very useful for describing the shape of a piece part or component, even though they have a distorted look. Three type of pictorial drawings are (Fig 1) These three lines which represent the mutually perpendicular • Isometric drawing edges are isometric axes. Generally those axes are kept • Oblique drawing in four positions. (Fig 3) • Perspective drawing
So to draw the isometric drawing, first draw the three mutually perpendicular edges, set other linear dimensions and complete the figure. (Fig 4)
Out of the above three types, isometric drawings are very Isometric and non-isometric lines: Fig 5 shows the much preferred by machine shop and metal working trades isometric view of a shaped block. Here all lines except AB, group. But perspective drawings are popular in civil BC and DE are parallel to isometric axis. Such lines which engineering group of trades. are parallel to isometric axes are called isometric lines Isometric drawing: In an isometric drawing the three whereas such lines AB, BC and DE which are not parallel mutually perpendicular edges of a cube are at an angle of to isometric axes are called non-isometric lines. 120° with each other. Instead of drawing the edges in the The length of non-isometric lines will not follow the scale above said way, first we can also start from point `a'. At this used for isometric lines. To prove this point consider the point also three mutually perpendicular edges met while non-isometric lines AB or BC. The true length of both AB two of these edges make 30° to horizontal, the other edge and BC is 5 cm while BC will be longer. Because of this is vertical. After drawing two 30° lines and one vertical line, reason non-isometric lines are drawn first by locating their parallel lines are drawn to complete cube. (Fig 2) starting and end points on isometric lines. 104 Copyright Free. Under CC BY License. • Mark the distances kg and dh on the top face of box. (Fig 7c) • Join the points ab, bc, ca, ag, bg and cg and complete the isometric view of the pyramid in box method. (Fig7c)
Off-set method of drawing a pyramid Example To locate the end points and to draw the non-isometric lines Same triangular pyramid (Fig 6) is considered for drawing two methods are employed. They are isometric view using offset method. • Box method • Draw an isometric square/rectangle considering the corners of the base of the pyramid. (Fig 8a) • Off-set method • With the help of Fig 6 (Plan) locate all the three corners Box method: The object is assumed to be inside a of the base P,Q and r using offset method. rectangular box. Starting and end points are located and marked. By joining the points isometric view is drawn. • Locate the position of vertex `O' on base by referring the Fig 6 (Plan) using the same offset method. (Fig 8b) Off-set method: This method is most suited for the objects consisting of number of planes at a number of different • Draw the vertical line 0'-0 to the height of the pyramid. angles. • Join the corners of the base. These methods are not only useful for isometric • Join the vertex 0' with the corners of the base and views involving non-isometric lines but also for complete the pyramid. (Fig 8c) the isometric views involving isometric lines.
Box method of drawing a pyramid Example Draw an isometric view for the triangular pyramid shown in Fig 6 using a box method.
Angles in isometric drawing: The angles of inclined surfaces will not have the value in the isometric drawing, but will be more in some cases and less in other cases. For example, in the isometric view of prism shown in Fig 9 the true value of all the angles is 90°. But in isometric drawing the angles are 60° in some cases and 120° in others.
• Construct a rectangular box to the overall size of the pyramid (Fig 7a) • Mark the distances ad and be from the plan of Fig 7b in the base of the box.
Engineering Drawing : (NSQF) Exercise 1.9.27 105 Copyright Free. Under CC BY License. Isometric circles: The term isometric circle refers to the Fig 13 shows the construction of isometric circle in 3 shape of circle in isometric view. An isometric circle will be different orientation by arc method. Four arcs are to be elliptical in shape as shown in Fig 10. While drawing drawn and the centres an C1, C2, B & D. While centre B isometric view of cylindrical features isometric circles will and D are the corner of the rhombus C1 and C2 are have to be used. (Fig11) intersection points of the longer diagonal with lines from points B or D to the mid point of the side of the rhombus.
Note: The arc method gives a clean ellipse, but this ellipse drawn this way will slightly deviate from true ellipse. It does not matter for our purpose.
The isometric circles can also be drawn using templates which can be bought from stationary shops. An isometric circle can be drawn either be plotting offset Isometric view of profiles: The profile M'N' of the block method or by arc method. shown in Fig 14 is irregular in nature. The isometric views Plotting method (Fig 12) of such lines may be drawn by offset method described earlier. The points 1',2',3' and 4' lie on the profile. Lines A'- 1', B'-2', C'-3', D'-4' are isometric lines and their length are same both in Fig 14 & Fig 15. After getting the points 1,2,3 & 4, they joined by smooth curve.
• Draw a square of side equal to the dia of circle and inscribe the circle. • Divide the circle into any number of equal parts and mark points such as 1,2,3,4,5,6,7,8 on the circle. • Through the points 1,2,3 etc draw lines parallel to the both the axis of cylinder. Note: In offset method more the number of • Draw isometric view of the square. points, better will be the accuracy of the curve.
• Mark points corresponding to 1,2,3....8 with isometric Isometric drawing of sphere: The Orthographic view of view of the square as points 1',2',3'....8'. a sphere seen from any direction is a circle of diameter • Join these points with a smooth curve to for an ellipse. equal to the diameter of the sphere. Hence, the isometric drawing of a sphere is also a circle of the same diameter. Note: The orientation of the isometric circle will depend upon the plane on which the The front view and the top view of a sphere resting on flat circular feature exists. surface are shown in Fig 16a. `O' as its centre, D is the diameter and P is the point of Arc method: Isometric circles drawn by offset method is contact with the surface. the ideal method of making isometric circles as the ellipse obtained this way is geometrically true. But by free hand we cannot get a clear line.
106 Engineering Drawing : (NSQF) Exercise 1.9.27 Copyright Free. Under CC BY License. Again, assume a horizontal section through the centre of the sphere. The isometric drawing of this circle is shown by the ellipse 3, drawn in a horizontal position around the same centre `O'. In all the three cases 1,2 & 3 the outermost points on the ellipse from the centre `O' is equal to 1/2 D. Thus, it can be seen that in an isometric drawing, the distances of all the points on the surface of a sphere from its centre are equal to the radius of the sphere. Hence, the isometric projection of a sphere is a circle whose diameter is equal to the true diameter of the sphere. (Fig 17) Also the distance of the centre of the sphere from its point Assume a vertical section the centre of the sphere. Its of contact with the flat surface is equal to the isometric shape will be a circle of diameter D. The isometric drawing radius OP of the sphere. of this circle are ellipses 1 & 2 Fig 16(b) drawn in two It is therefore of the utmost importance to note that different vertical positions around the same centre `O'. The isometric scale must invariably be used while drawing major axis in each case is equal to D. The distance of the isometric projection of solids in conjunction with spheres point P from the centre `O' is equal to the isometric radius or having spherical parts. of the sphere.
Practice of isometric views
Draw the following isometric figures (Ex.1 to 8) in A3/A4 • Draw two vertical lines parallel to the line AH through Sheets. Follow the procedure given wherever necessary. points B and D. Procedure • Similarly draw two more lines parallel to AB and AD through point H. 1 Draw the isometric drawing of a rectangular prism • Mark G and E the intersecting points. of base 30 mm x 40 mm and the height 60 mm. (Fig1) • Draw lines parallel to GH and HE through points G and E intersecting point is F. • Draw lines parallel to AB & AD through points D and B respectively intersecting at C. • Join CB & CD with dash lines. • Join F and C also with dash lines. • Rub off the construction lines and complete the prism.
2 Draw the isometric view of the stepped block given in Fig2. • Draw the isometric view of a rectangular prism of dimensions equal to the overall size of the block 45 x 25 x 30 mm. • Draw the three isometric axes through point `A'. • Draw the lines JD, DE, EF, FH, HI and IJ using the • Mark AB = 15 mm, AD = 30 mm and AH = 50 mm measurements given in the figure. representing the three sides of prism. • Rub off SR, RD, SJ, SH and RF. Engineering Drawing : (NSQF) Exercise 1.9.27 107 Copyright Free. Under CC BY License. • Darken the remaining lines of the stepped block. Note: All construction lines should be in thin lines. After completion of the isometric views, in each case erase the unwanted lines and construction lines.
With the experiences gained in previous exercises of drawing isometric views, draw the following exercises 4 & 5 and complete the same. 4 (Fig 4)
3 Draw the isometric view of the components shown. (Fig 3)
5 (Fig 5)
• Draw the stepped block as per dimension. Follow the procedure given in the previous Ex.No.2. • Mark points UTSV as per dimension on the top of the surface EDGF (Fig 3b) 6 Draw the isometric view of the machined block • Join points UTSV. having non-isometric lines. (Fig 6a) • Project vertically downwards from the points UTSV and • Draw an isometric box. (Fig 6b) obtain the point WXYZ at bottom surface such that UW, TX, SY & VZ are equal to 10 mm. Join the point WXYZ • Mark point A on PS at a distance of 15 mm from P. and draw the thick lines which are all visible and dotted • Draw line AB = 25 mm parallel to PQ. lines which are not visible. 108 Engineering Drawing : (NSQF) Exercise 1.9.27 Copyright Free. Under CC BY License. • From B, draw a vertical line cutting RS at L. • Mark point D on US such that UD = 20 mm. • Draw a line DC parallel to UT equal to AB. • Join AD, BC and CL to complete the required isometric view of the block. • Remove the extra lines and darken the required visible edges. • Show hidden edges by dashed lines.
Draw the isometric drawing of the following slant cut blocks. (Fig 8) • In each case draw the isometric view of a rectangular prism to the overall sizes of the each block. • Follow the procedure adopted in the previous exercises and complete the each isometric view of the blocks. • Remove the unwanted lines, draw the remaining lines 7 Draw the isometric view of the `V' block. (Fig 7a) thick and hidden lines as required. Complete the • Draw the isometric view of a rectangular box of size 50 figures. x 40 x 30. • Assume the missing dimensions if any proportionally. • On the face ABFE, draw the lines JN & LN by offset method. • Similarly draw lines KP & MP. • Join ML, KJ and PN. • Erase construction lines and make the remaining line thick and dashes according to the drawing.
Engineering Drawing : (NSQF) Exercise 1.9.27 109 Copyright Free. Under CC BY License. Pictorial drawing (Oblique drawing)
Oblique drawings are yet another type of pictorial Projection of edges such as AE, DH, BF and CG which are projections, they differ from isometric drawings in two perpendicular to the plane of projection will measure ways. differently depending on the angle of inclination of the projectors. If the inclination of the projectors is 45° the – In oblique drawing, projections are oblique (inclined) to projections of these edges measure to their true lengths. the plane of projection. whereas in isometric projections If the angle is less than 45° the projection of such projectors are perpendicular to the plane of projection. perpendicular edges will measure less than the true length, (Fig 1) if the angle of inclination of the projectors is greater than 45°. Projection of such perpendicular edges will measure more than the true length. Oblique projections nevertheless have an unique advantage what we want to make pictorial drawings of object having curved features. For making isometric views of a curved feature we have first to draw their orthographic views in order to find out the offsets of points lying on the curve. But this difficult procedure is not necessary in the case of oblique views. For example the component shown in Fig 3 has several curved features. While drawing oblique view of this component the curved features are drawn to true shape using compass. This is relatively easier method in comparison to the drawing of the same component in isometric view.
– In an oblique drawing one of the principal faces of the object is kept parallel to the plane of projection, but in isometric, none of the faces of the object is parallel to the plane of projection.
Even though one of face of the object is positioned parallel to the picture plane, we still get a pictorial view and the projections are Inclination of projectors: While projectors can have any inclined to both HP and VP. angle of inclination, usually oblique views are drawn to either 45° or 30°. The inclined lines in the oblique drawings Because one of the principle faces of the object is parallel are called receding lines (Fig 4) and they are more to the plane of projection, in the oblique projection, the commonly drawn to 45°. The scale of lines along receding projection of this face and faces parallel to it will appear in may be 1:1 (true lengths) or 1:2 (half of the true length). true size and shape. In the oblique projection of a prism is Oblique drawing drawn to 1:1 (Fig 5) are called as cavalier shown in Fig 2, the faces ABCD and EFGH are parallel to projections and those drawn to 1:2 (Fig 6) are called as the plane of projection and they appear to be true in size cabinet projections. These two terms are of academic and shape. The other four faces which are perpendicular interest only and mostly we refer these views as oblique to the plane of projection do not appear in true shape. (all projections/drawings only. these four faces are seen as parallelogram) However the vertical edges of these faces are parallel to the plane of In comparison a cabinet projection will look less distorted projection and hence the projection of these edges will than a cavalier projection. measure to their true lengths.
110 Engineering Drawing : (NSQF) Exercise 1.9.27 Copyright Free. Under CC BY License. Object positioning in oblique drawing: Remember to position the object in such a way as to make best use of the advantage offered by oblique projection. The face that has the maximum curved details should be placed parallel to the plane of projection. See example in Fig 8.
Another point to note is as far as possible, place the longest dimension parallel to the plane of projection. (Fig9a & b)
Procedure for drawing oblique views: The procedure for creating oblique drawing is very much similar to that for drawing isometric views. To make isometric view we start from drawing three isometric axes at the desired orientation. In oblique drawing also we start by drawing three axes at the desired orientation. But here two of the axes are perpendicular to each other while the third axis (receding axis). Make 45° or 30° to the horizontal. The orientation Few examples of oblique drawings are shown in Fig 10. of the axes may be any one of the four possibilities given in the figure 7.
Engineering Drawing : (NSQF) Exercise 1.9.27 111 Copyright Free. Under CC BY License. Method of perspective views
Perspective (from Latin: perspicere "to see through") in the graphic arts is an approximate representation, generally on a flat surface (such as paper), of an image as it is seen by the eye. The two most characteristic features of perspective are that objects appear smaller as their distance from the observer increases; (Fig 1) and that they are subject to foreshortening, meaning that an object's dimensions along the line of sight appear shorter than its dimensions across the line of sight.
Two-point perspective A drawing has two-point perspective when it contains two vanishing points on the horizon line. In an illustration, these vanishing points can be placed arbitrarily along the horizon. (Fig 1&2) Two-point perspective can be used to draw the same objects as one-point perspective, rotated: looking at the corner of a house, or at two forked roads shrinking into the distance, for example. One point represents one One-point perspective set of parallel lines, the other point represents the other. A drawing has one-point perspective when it contains only Seen from the corner, one wall of a house would recede one vanishing point on the horizon line. (Fig 1&2) This towards one vanishing point while the other wall recedes type of perspective is typically used for images of roads, towards the opposite vanishing point. railway tracks, hallways, or buildings viewed so that the front is directly facing the viewer.
112 Engineering Drawing : (NSQF) Exercise 1.9.27 Copyright Free. Under CC BY License. Three-point perspective Three-point perspective is often used for buildings seen from above (or below). (Fig 1&2) In addition to the two vanishing points from before, one for each wall, there is now one for how the vertical lines of the walls recede. For an object seen from above, this third vanishing point is below the ground. For an object seen from below, as when the viewer looks up at a tall building, the third vanishing point is high in space.
Engineering Drawing : (NSQF) Exercise 1.9.27 113 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.9.28 Engineering Drawing
Method of presentation of engineering drawing - Orthographic view
114 Copyright Free. Under CC BY License. Engineering Drawing : (NSQF) Exercise 1.9.28 115 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.10.29 Engineering Drawing
Symbolic representation - different symbols used in the trades - Fastener (bolts, nuts and rivets)
Introduction 1 Materials Conventions are the graphical symbols used while making 2 Equipments/Instruments/Engineering Components drawings to indicate
1 Fasteners (Rivets, Bolts and Nuts) 4 Electrical and Electronic elements 2 Bars and Profile section 5 Piping joints and Fittings 3 Weld, Brazed and soldering joints
Fasteners (bolts, nuts and rivets)
Grade Identification Material Grade Identification Material Marking Marking
Carbon Steel Carbon Steel Carbon Steel Quenched & Tempered Carbon Steel
Atmospheric Corrosion Carbon Steel Quenched & Resistant Steel, Quenched Tempered & Tempered
Atmospheric Corrosion Resistant Steel, Carbon Steel Quenched & Tempered
Carbon Steel, Quenched & Tempered Medium Carbon Steel
116 Copyright Free. Under CC BY License. Grade Identification Material Marking
Medium Carbon Steel Quenched & Tempered
Medium Carbon Steel Quenched & Tempered
Medium Carbon Steel Quenched & Tempered
Medium Carbon Steel Quenched & Tempered
Medium Carbon Steel Quenched & Tempered
Rivet Symbol • In case of large drawings where no. of rivets are used, it is not necessary to draw all rivets. • For this, gauge lines are drawn and location of rivets are shown by line symbol as per I.S.I.
Sl.No Object Symbol Sl.No Object Symbol
1 Shop SNAP Headed rivets 6 Site CSK (Near side) rivets
2 Shop CSK (Near side) rivets 7 Site CSK (Far side) rivets
3 Shop CSK (Far side) rivets 8 Site CSK (Both side) rivets
4 Shop CSK (Both side) rivets 9 Open Hole
5 Site SNAP Headed rivets
Engineering Drawing : (NSQF) Exercise 1.10.29 117 Copyright Free. Under CC BY License. Rivet symbols Because many engineering structures are too large to be built in the shop, they are built in the largest units possible and then are transported to the desired location. Trusses are common examples. The rivets driven in the shop are called shop rivets, and those driven on the job are called field rivets.
118 Engineering Drawing : (NSQF) Exercise 1.10.29 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.10.30 Engineering Drawing
Symbolic representation of bars and profile sections
119 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.10.31 Engineering Drawing
Symbolic representation of weld, brazed and soldered joints
1 Symbolic representation of supplementary Convention used for Welded joints welding symbols
S.no Designation Illustration Symbol
1 Fillet
2 Square butt
3 Single V-butt
2 Symbolic representation of Positioning of welding 4 Double V-butt symbols
5 Single U-butt
6 Double U-butt
7 Single bevel butt
8 Double bevel butt 3 Symbolic representation of End view of joint, its symbolization and front view of its symbolization 9 Single J-butt
10 Double J-butt
11 Stud
12 Bead edge or seal
13 Sealing run
14 Spot
15 Seam
16 Stitch
17 Plug weld
120 Copyright Free. Under CC BY License. 4 Brazed and soldered joints
Engineering Drawing : (NSQF) Exercise 1.10.31 121 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.10.32 Engineering Drawing
Symbolic representation of electrical and electronic elements
Conventions used for electrical and electronic elements
S.No. Particulars Symbols S.No. Particulars Symbols
1 D.C. 11 Cell
2 A.C.
12 Battery
3 Positive
13 Single pole single 4 Negative throw switch
5 Single Phase A.C. 50 Hz 14 Push-button switch
6 Three Phase A.C., 50 Hz
15 Energy meter
7 A.C. / D.C.
16 Alternator
8 3-Phase line
17 Generator
9 Neutral line
18 D.C. Motor
10 Earth
122 Copyright Free. Under CC BY License. S.No. Particulars Symbols S.No. Particulars Symbols
29 Ceiling Rose 19 A.C.Motor Single 2-pin, 3-pin phase
30 Over head line 20 3-phase squirrel cage motor
31 Aerial
21 3-phase slip ring motor
32 Voltmeter
22 Capacitor: Fixed, variable 33 Ammeter
23 Electrolytic Capacitor
34 Ohm Meter
24 Two-way switch 35 Watt Meter
36 Lamp
25 D.P.D.T. Switch
37 Fan regulator
26 Fuse: ordinary cartridge 38 Electro Magnet
27 Link
39 Relay 28 Socket 2 pin, 3 pin
Engineering Drawing : (NSQF) Exercise 1.10.32 123 Copyright Free. Under CC BY License. S.No. Particulars Symbols S.No. Particulars Symbols
40 Electric bell 51 Rectifier
41 Buzzer 52 Trimmer: Padder
42 Contacts - NO, NC
53 Ganged Capacitor
43 3-phase contactor
54 Main transformer 44 Connections: with multiple star, Delta secondary winding
45 Choke 55 Auto transformer
46 Transformers
56 Silicon Bilateral switch (SBS)
47 Carbon microphone
57 S.C.R.
48 Loudspeaker
58 U.J.T 49 Resistor : Fixed
59 F.E.T. N-Channel 50 Resistor: variable
124 Engineering Drawing : (NSQF) Exercise 1.10.32 Copyright Free. Under CC BY License. S.No. Particulars Symbols S.No. Particulars Symbols
68 AND gate 60 F.E.T. P-Channel
69 NAND gate
61 TRAIC
70 Ex-OR gate
62 DIAC 71 Operational amplifier
63 NPN Transistor 72 Ex-NOR gate
73 Flip - flop 64 PNP transistor
74 Differential Amplifier 65 NOT gate
66 OR gate 75 Light emitting diode
67 NOR gate 76 Photo diode
Engineering Drawing : (NSQF) Exercise 1.10.32 125 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.10.33 Engineering Drawing
Symbolic representation of piping joints and fittings
Isometric and orthographic symbols for pipe fittings
S. No. Description Isometric symbol (right face) Orthographic symbol
Screwed Flanged Screwed Flanged
1 Joint/Coupling
2 Reducer
3 900 elbow
(i) Turned up
(ii) Turned down
4 Tee
(i) Turned up
(ii) Turned down
5 Cross
6 Bend
7 Plug (female)/(dead end)
8 Plug (male)
9 Union
10 Hose nipple
126 Copyright Free. Under CC BY License. Image Valves Butt weld Symbol Flanged Symbol
Gate
Globe
Ball
Plug
Butterfly
Needle
Engineering Drawing : (NSQF) Exercise 1.10.33 127 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.11.34 Engineering Drawing
Projections - concept of axes plane and quadrant
Graphics are preferred by engineer's and craftsman to From Fig 1 & 2, it is clear that there are different ways of communicate their ideas. When graphics are used for describing the shape of a part on a paper. Figure 1 is called communication it is called graphical language. Those who as Multiview drawing or Orthographic drawing and the do not have the knowledge of this language are professionally method adopted in figure 2 is called pictorial drawing. The illiterate. different views in a multiview drawing are called as The saying that "A picture is worth a thousand words" is 'Orthographic views' or Orthographic projections. very much relevant in technical work. To describe the shape of a part in engineering drawings, An engineering drawing conveys many different types of multiview or orthographic view method is preferred as only information of which the most important thing is the shape Orthographic view can convey the true shape of the object. of the object. Fig 1 shows a sample drawing. In this drawing Whereas in pictorial drawing through this shape is easily the shape of the part is represented by three views. understood and it is distorted. To emphasise this point, see Fig 3, wherein a cube with a circular hole is represented pictorially. We know that all corners of the cube are of 90°. But in the pictorial drawing in Fig 3, the same 90° is represented at some places by acute angles and at some other places by obtuse angles.
For an untrained person it will be very difficult to conceive the shape of the object from the above drawing. Projection: Projection is commonly used term in But in Fig 2, the same object is shown pictorially in a draughtsman’s vocabulary. In the context of engineering different ways and the shape is easily understood even by drawing, projectors means image and it is comparable to a layman. the image formed on the retina of the eyes. (Projection can also be compared to the image of the object on the screen, where the film is projected (by the cinema projector) by the light rays. Projection or images can also be formed in between the eyes and the object by keeping a transparent plane. (Fig 4) In this figure 4 the rays from the object converge to the eyes and this image (Projection) is smaller than the object. However if the rays are parallel as in the case of rays coming from the sun, the image (Projection) will be of the same size as that of the objects. Such a projection is called orthographic projection. The parallel lines/rays drawn from the object are called projectors and the plane on which image is formed is called plane of projection. In orthographic projection, the projectors are perpendicular to the plane of projection. (Fig 5)
128 Copyright Free. Under CC BY License. The two views thus required are to be obtained on two different planes which are mutually perpendicular (one HP and one VP) with the object remaining in the same position. The projection or the view obtained on the horizontal plane is called the top view or plan and the view obtained on the vertical plane is called elevation. First angle and third angle projection: One vertical plane (VP) and one horizontal plane (HP) intersect at right angles to each other. (Fig 7)
All the four quadrants have one HP and one VP formation. As per convention in mathematics, the quadrants are Orthographic projection: The term orthographic is numbered as 1st, 2nd, 3rd and 4th. These four quadrants are projection derived from the words, Ortho means straight or called four dihedral angles, namely 1st angle, 2nd angle, 3rd at right angles and graphic means written or drawn. The angle and 4th angle. projection comes from the Old Latin words PRO means forward and Section means to throw. The orthographic To draw two views of an object, we assume that the object projection literally means "Throw to forward", "drawn at is placed in any one of the quadrant/angles, 1st angle & 3rd right angles" to the planes of projection. angle Fig 8a, 9a and its plan and elevation projected to the respective planes. An orthographic system of projection is the method of representing the exact shape and size of a three dimensional Now to make it possible to draw the two views (Plan & object on a drawing sheet or any other plain surface such elevation) in one plane i.e the plane of the drawing paper, as drawing board. the horizontal plane is assumed to be unfolded in clockwise direction through 90° Fig 8b & 9b. We proceed this way, A single orthographic view of an object will show only two when the views are made. When the object is placed in the of its three dimensions. The view in figure 6 shows only the 2nd or fourth quadrant the plan and elevation will get super length and height of the object only. imposed (one up on the other) Fig 10a & b. Therefore, it becomes necessary to have an additional view to show the missing dimensions (width). Therefore, we have to make two views to represent the three dimensions of an object.
Engineering Drawing : (NSQF) Exercise 1.11.34 129 Copyright Free. Under CC BY License. Due to this reason the 2nd and 4th angle are not used for making engineering drawings as the three dimensions cannot be easily identified. Hence for representing the three dimension of the object, we assume the object is placed either in 1st angle and in 3rd angle (Fig 11 & 12) respectively The placement of plan and elevation when the horizontal plane is unfolded will be different in these two systems. It may be observed in Fig 13 that in the first angle projection plan (top views) will be directly below the elevation, whereas in 3rd angle projection plan lies directly above the elevation. (Fig 14) Views can be drawn in any one of these two methods. However Bureau of Indian Standard (BIS) has recommended the first angle method to be used in our country.
130 Engineering Drawing : (NSQF) Exercise 1.11.34 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.11.35 Engineering Drawing
Projections - Orthographic projection
Procedure In this exercise the faces of prism are parallel to the planes of projection. Therefore all the lines orthographic projection Method 1 are vertical and horizontal lines only. Draw the orthographic projection (front, top and side views) Visualise the shape of the object and imagine the shape of the square sheet (40 mm side) kept perpendicular to HP description of views. Surface ABCD (Fig 2B) only visible and parallel to VP. (I angle) (Fig 1) from the elevation. At the same time all the four sides of ABCD are isometric lines. Therefore in the elevation a rectangle of 40 x 30 mm is seen.
• Draw the xy line. • Draw the square with its centre 40 mm above the xy line and one edge parallel to xy line. • Mark the corners of the figure a', b', c' & d'. This will be the front of the square. • Draw the vertical projectors from a'b' downward beyond the xy line. • Draw a horizontal line dc at a distance of 20 mm below the xy line. Line dc will be the plan. • Draw a X'Y' line at a convenient distance from b'c', intersecting the xy line at `0'. • Project the top to the X Y line meeting at e. • By arc method transfer Oe to xy and mark the point `f' • Draw xy line of convenient length. (Fig 2B) at a" and d" respectively. Now the line a"d" is the side • Draw a rectangle a'b'c'd' on the xy line. This will be the view. front view of the prism. Method 2 : Rectangular prism • Project the vertical sides of the front view (a'd' and b'd') Draw the Top, Front and side views of the rectangular prism downwards beyond xy line. of base 30 x 20 mm and height 40 mm. (Fig 2A) • Draw a horizontal line fg approximately 20 mm below xy line. 131 Copyright Free. Under CC BY License. • Draw a rectangle fgba of 35 x 20 mm size. This will be • Draw projectors from elevation and side view and the plan of the prism. complete the plan. • Project points b' and c' horizontally a convenient length (Three lateral faces are visible of which one is of true to the right side of the elevation. shape and the other two are fore shortened) • Transfer the width of top view gb by arc and locate points Method 4 : Cylinder e"d" on the xy line. Draw the top, front and side view of a cylinder of diameter • Project e"d" vertically up and locate points f"a"d"e" is 20 mm and length 30 mm. (Fig 4A) the left side view of the prism.
Method 3 : Hexagonal prism Draw the three views of the hexagonal prism shown in Fig3A. From the position described above, it is clear that the hexagonal face of the prism is parallel to AVP. Therefore the end view is a true hexagon and hence this view should be drawn first. • Draw the side view (hexagonal of side 25 mm) with one side on HP line. (Fig 3B) • Draw horizontal projectors from side view and complete the front view. (in the front view two lateral faces are visible, but they are fore shortened)
In this problem the circular faces are parallel to VP. Therefore the front is a circle resting on XY line. Plan an end views are rectangles of size 30 mm x 20 mm.
132 Engineering Drawing : (NSQF) Exercise 1.11.35 Copyright Free. Under CC BY License. • Draw the circle of diameter 40 mm touching XY line. In this front view, three triangular faces are seen and all of (Fig4B) them are fore-shortened. • Draw the plan projecting it from the elevation. • Mark the centre of hexagon (Point P) and draw lines from P to the six corners of the hexagon. Now this is • Draw the end view by drawing projection on it, from the the required plan. (Fig 6B) plan and elevation. • Project this P from plan upwards and mark P' at a • Draw the top, front and side views of a cylinder whose distance of 75 mm from XY line. base diameter 35 mm and height 50 mm when its position is as shown in Fig 4C. • Mark the points f', a'b'c' etc... on XY line by projecting the corresponding points from plan. Method 5 : Cone • Join the P' with f', a',b',c' etc and complete the required Draw the multi-views of the cone shown in the Fig 5A. elevation. Follow the procedures of the earlier exercises and draw the • Draw projectors from elevation and plan to complete the multi-views. (Fig 5B) required side view.
Method 7 Method 6 : Regular hexagonal pyramid Identify the surfaces of the block shown in the isometric Draw the Orthographic views of a regular hexagonal pyra- view with the corresponding multi-views and fill the numericals mid of side 20 mm and height 40 mm given its position as in the given tabulation column. (Fig 7) below. (Fig 6A) The surfaces are parallel and perpendicular to the plane of – standing vertically with its base on HP and one side of projection. the hexagonal base parallel to VP. • Study the isometric view and the corresponding multi- The pyramid has 6 triangular faces and one hexagonal views carefully. base. The top view will show the true shape of the base and other six triangular faces are fore-shortened. Engineering Drawing : (NSQF) Exercise 1.11.35 133 Copyright Free. Under CC BY License. • You may observe that the surfaces seen in one view are • Similarly the surface `A' seen from the top of the represented by lines in other two views. isometric views is numbered as `10' in the plan of the multi-views, whereas the full surface area is visible. • In this exercise the surface `A' shown in isometric view is seen as a line in the front elevation and numbered as When a surface is parallel or perpendicular to the plane of `5' in the front view of the corresponding multi-views. projection vice-versa in a multi-views drawing, full area of the surface will be seen in any one the three views (plan, • The same surface `A' in the side view is seen as a line elevation and side view) and in other two views the and numbered `6' in the side view of the multi-views. corresponding line of the surface will be seen.
Method 8 Identify the surfaces of the block with slope cuts shown in • In this exercise, the surface `B' is seen as a surface in isometric view with the corresponding multi-views and fill front view and top view, numbered in multi-views as 7 & the tabulation column. (Fig 8) 8 respectively. Surfaces B and F are inclined to HP and parallel to VP. • The same surface `B' in the side view is seen as a line • You may observe that the surface inclined to one plane and numbered as 19 in the multi-views which are shown is seen in other two views as fore-shortened area of the in tabular column. Study the drawing carefully and fill surface and in other view the corresponding line of the up the other columns. surface is visible.
Method 9 (Fig 9) Identify the surfaces of the block shown in Isometric view • Seen from top of the isometric view the fore-shortened with the corresponding multi-views and fill in the tabulation area of the surface is seen and numbered as 5 in the top column. (Fig 9) view of the multi-view. Similarly in side view it is The surface is inclined to three planes HP, VP & AVP. numbered as 7 in multi-view. • In this exercise you may observe that the surface `A' is When a surface of the object is inclined to all the planes, inclined to all the three planes. the complete fore-shortened surface will be seen in all the three views. • When you visualise the surface `A' in the front view of the isometric view, the fore-shortened area of the surface is • Fill the other columns and complete the exercise. seen and numbered as 2 in the multi-view. 134 Engineering Drawing : (NSQF) Exercise 1.11.35 Copyright Free. Under CC BY License. Method 10 Draw the isometric view (Fig 10) and also draw the three views in the work book.
line joining `D' and `E', also the line joining back bottom Orthographic projection shows the shape of a component surfaces are appearing in the side view by hidden line. by drawing number of views each looking at different side (Fig13) of the component. Arrange views as stated earlier with uniform gap between A minimum of two views are required to represent a views. (Fig 13) component. In order to clarify clearly the internal and external details a minimum of three views are to be drawn. They are: • Elevation or Front view or Front elevation. (F) • Plan or Top view. (P) • Side view or side elevation or end elevation. (S) In the Fig 10, surface `A' is only seen when looking at the front of the figure. All the lines in the isometric view are isometric lines. Therefore in the orthographic projection, the front view will be like this. (Fig 11) In the plan surfaces `C', `D' and `F' are visible and the bottom surface will not visible. The line joining the two surfaces will not visible. The line joining the surfaces will appear in the plan by hidden line. (Fig 12) In the side view surface `B' is visible and surfaces `E' and back bottom surfaces are invisible. Due to this reason the Engineering Drawing : (NSQF) Exercise 1.11.35 135 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.11.36 Engineering Drawing
Projection - Method of 1st angle and 3rd angle projections (Definition and difference)
An orthographic system of projection is the method of The two views thus required are to be obtained on two representing the exact shape and size of a three dimensional different planes which are mutually perpendicular (one HP object on a drawing sheet or any other plain surface such and one VP) with the object remaining in the same position. as drawing board. The projection or the view obtained on the horizontal plane is called the top view or plan and the view obtained on the rd 3 Angle projection (Fig 1) vertical plane is called elevation. First angle and third angle projection: One vertical plane (VP) and one horizontal plane (HP) intersect at right angles to each other. (Fig 3)
1st Angle projection (Fig 2)
All the four quadrants have one HP and one VP formation. As per convention in mathematics, the quadrants are numbered as 1st, 2nd, 3rd and 4th. These four quadrants are called four dihedral angles, namely 1st angle, 2nd angle, 3rd angle and 4th angle. To draw two views of an object, we assume that the object is placed in any one of the quadrant/angles, 1st angle & 3rd angle (Fig 4a & 5a) and its top and front view projected to the respective planes. Now to make it possible to draw the two views (Front & Top view) in one plane i.e the plane of the drawing paper, the horizontal plane is assumed to be unfolded in clockwise direction through 90° (Fig 4b & 5b) . We proceed this way, when the views are made. When the object is placed in the 2nd or fourth quadrant the front and top will get super imposed (one up on the other) (Fig 6a & 6b).
A single orthographic view of an object will show only two of its three dimensions. The view in figure.1 front view shows only the length and height of the object only. Therefore, it becomes necessary to have an additional views of top and side views to show the missing dimensions (width). Therefore, we have to make two views to represent the three dimensions of an object.
136 Copyright Free. Under CC BY License. Due to this reason the 2nd and 4th angle are not used for making engineering drawings as the three dimensions cannot be easily identified. Hence for representing the three dimension of the object, we assume the object is placed either in 1st angle and in 3rd angle (Fig 7&8) respectively The placement of front and top views when the horizontal plane is unfolded will be different in these two systems. It may be observed in Fig 8, that in the first angle projection plan (top views) will be directly below the front view, whereas in 3rd angle projection top view lies directly above the elevation. (Fig 10) Views can be drawn in any one of these two methods. However Indian Standard (BIS) has recommended the first angle method to be used in our country.
Engineering Drawing : (NSQF) Exercise 1.11.36 137 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.11.37 Engineering Drawing
Projection - Symbol of 1st angle and 3rd angle projection as per IS specification
1 a Draw the symbol for 1st angle projection as per IS 2 a Draw the symbol for 1st angle projection as per IS specification, if bigger dia D is 50 mm. specification, if smaller dia D/2 is 20 mm. b Draw the symbol for 3rd angle projection as per IS b Draw the symbol for 3rd angle projection as per IS specification, if bigger dia D is 40 mm. specification, if smaller dia D/2 is 15 mm.
138 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.12.38 Engineering Drawing
Drawing of orthographic projection from isometric projection
Draw Orthographic views in first angle projection
139 Copyright Free. Under CC BY License. Draw three views of the block in 1st angle projection.
Draw three views of the block both in 1st and 3rd angle projection.
Draw three views of the given block in 3rd angle projection.
Draw three views of the block in 1st angle projection.
Draw three views of the given block in 3rd angle projection.
140 Engineering Drawing : (NSQF) Exercise 1.12.38 Copyright Free. Under CC BY License. Draw three views of the given block in 1st and 3rd angle Draw three views of the given block in 1st angle projection. projection.
Draw three views of the given block in 3rd angle projection.
Draw three views of the given block in 1st angle projection.
Draw three views of the given block in 3rd angle projection.
Engineering Drawing : (NSQF) Exercise 1.12.38 141 Copyright Free. Under CC BY License. 142 Engineering Drawing : (NSQF) Exercise 1.12.38 Copyright Free. Under CC BY License. For Engineering Trades Exercise 1.13.39 Engineering Drawing
Reading of fabrication drawing for sheet metal worker trade Funnel Wire ring on the flange
Cylinderical shape by a round mandrel Curved edge to be fixed using a gauge
Shoulder with ferrule Upset the flange
Curve on the flange for wiring
Body
143 Copyright Free. Under CC BY License. Handle Funnel
Reading of fabrication drawing for welder trade
Basic welding positions – Overhead position (Fig 4) – Flat or down hand position (Fig 1)
All welding action takes place in the molten pool, formed – Horizontal position (Fig 2) in the welding joint/welding line. The position of the welding joint line and the weld face in respect of ground axis indicates the welding position. All joints may be welded in all positions. Plate welding Position:
EN ASME Welding Position Groove Fillet Groove Fillet
Flat PA PA 1G 1F Horizontal PC PB 2G 2F Vertical PG/PF PG/PF 3G 3F – Vertical position (Vertical up and down) (Fig 3) Overhead PE PD 4G 4F Pipe welding Position:
EN ASME Welding Position Groove Groove Flat PA 1G Horizontal PC 2G Multiple position PF/PG 5G Inclined (All position) H-LO45 6G
144 Engineering Drawing : (NSQF) Exercise 1.13.39 Copyright Free. Under CC BY License. Reading of fabrication drawing for carpenter trade
Panel door (Fig 1) Window frame (Fig 3)
Parts of panel door (Fig 2)
Engineering Drawing : (NSQF) Exercise 1.13.39 145 Copyright Free. Under CC BY License.